1
PSYCHOLOGICAL TESTING AND ASSESSMENT
Testing and Assessment
 Roots can be found in early twentieth century in France 1905
 Alfred Binet published a test designed to help place Paris school children
 WW1, military used the test to screen large numbers of recruits quickly for intellectual and
emotional problems
 WW2, military depend more on tests to screen recruits for service
Psychological Testing and Assessment Defined
Psychological Testing
Process of measuring psychology-related
variables by means of devices/procedures
designed to obtain a sample of behavior
Psychological Assessment
Gathering & integration of psychology-related data
for the purpose of making a psychological evaluation
accomplished with tools.
Difference between Psychological Testing and Assessment
Point of
Testing
Assessment
Difference
Objective
To obtain some gauge,
To answer a referral question, solve problem or arrive at a
usually numerical in nature decision thru the use of tools of evaluation
Process
Testing may be
Typically individualized
individualized by group
Role of
Tester is not the key into the Key in the process of selecting tests as well as in drawing
Evaluator
process; may be substituted conclusions
Skill of
Requires technician-like
Typically requires and educated selection, skill in
Evaluator
skills
evaluation, thoughtful organization and integration of data
Outcome
Typically yields a test score Entails logical problem-solving approach to answer a
referral question
Process of Assessment
1
2
3
4
Referral for Assessment
Meeting
Selection
Formal Assessment
Teacher, school
The assessor
selection of the
the assessor
psychologist
prepares for the
instruments or
writes a report of
counsellor, judge,
assessment by
procedures to
the findings that
clinician, or corporate
selecting the tools
be employed
is designed to
human resources
of assessment to be
answer the
specialist.
used.
referral question.
Three Approaches of Assessment
1. COLLABORATIVE PSYCHOLOGICAL ASSESSMENT
 assessor and assessee work as partners from initial contact through final feedback
2. THERAPEUTIC PSYCHOLOGICAL ASSESSMENT
 self-discovery and new understandings are encouraged throughout the assessment process
3. DYNAMIC PSYCHOLOGICAL ASSESSMENT
2

follows a model (a) evaluation (b) intervention (a) evaluation. Provide a means for evaluating
how the assessee processes or benefits from some type of intervention during the course of
evaluation
THE TOOLS OF PSYCHOLOGICAL ASSESSMENT
The Test
 a measuring device or procedure
 psychological test: a device or procedure designed to measure variables related to psychology
(intelligence, personality, aptitude, interests, attitudes, or values)
 Psychological tests and other tools of assessment may differ with respect to a number of variables,
such as content, format, administration procedures, scoring and interpretation procedures, and
technical quality
Ways that TESTS differ from one another
1. Content
 Subject matter of the test
 vary with the focus of the particular test
 may differ widely in item content.
a) test developers might have entirely different views
b) test developers come to the test development process with different theoretical orientations
2. Format
 refers to the form, plan, structure, arrangement, and layout of test items as well as to related
considerations such as time limits.
a) also referred to as the form in which a test is administered (pen and paper, computer, etc)
Computers can generate scenarios.
b) term is also used to denote the form or structure of other evaluative tools, and processes, such
as the guidelines for creating a portfolio work sample
3. Administrative Procedures
 some test administrators have an active knowledge
o some test administration involves demonstration of tasks
o usually one-on-one
o trained observation of assessee’s performance
 some test administrators don’t even have to
o usually administered to larger groups
o test takers complete tasks independently
4. Scoring and Interpretation Procedures
 Score: a code or summary statement, usually (but not necessarily) numerical in nature, that
reflects an evaluation of performance on a test, task, interview, or some other sample of
behaviour
o Scoring: process of assigning such evaluative codes/ statements to performance on tests,
tasks, interviews, or other behavior samples.
o One type of score: cut score
3

cut score: reference point, usually numerical, derived by judgement and used to divide a
set of data into two or more classifications.
o who scores it
a) self-scored by testtaker
b) computer
c) trained examiner
5. Psychometric soundness/ technical quality
 Psychometrics: the science of psychological measurement.
o referring to to how consistently and how accurately a psychological test measures what it
purports to measure
 Utility: refers to the usefulness or practical value that a test or other tool of assessment has for a
particular purpose.
Q: State the Pros and Cons
The Interview
 method of gathering information through direct communication involving reciprocal exchange
 interviewer in face-to-face is taking note of: (a) verbal language; (b) nonverbal language (body
language movements, facial expressions in response to interviewer, the extent of eye contact,
apparent willingness to cooperate; (c)how they are dressed (neat vs sloppy vs inappropriate)
 interviewer over the phone taking note of: changes in the interviewee’s voice pitch, long pauses,
signs of emotion in response
 ways that interviews differ: (a) length, purpose, and nature; (b) in order to help make diagnostic,
treatment, selection, etc
Q: What are the Pros and Cons?
 Panel Interview
o Also referred as board interview
o an interview conducted with one interviewee with more than one interviewer
o Advantage: any idiosyncratic biases of a lone interviewer will be minimized
o Disadvantage: utility; the cost of using multiple interviewers may not be justified
The Portfolio
 files of work products: paper, canvas, film, video, audio, etc
 samples of ones abilities and accomplishments
 In education:
o the best evaluation of a student’s writing skills can be accomplished not by the administration
of a test, but by asking the student to compile a selection of writing samples.
o a tool in the hiring of instructors (may consist of various documents such as lesson plans,
published writings, and visual aids developed expressly for teaching certain subjects.
Case History Data
 records, transcripts, and other accounts in written, pictorial or other form that preserve archival
information, official and informal accounts, and other data and items relevant to assessee
o sheds light on an individual's past and current adjustment as well as on events and
circumstances that may have contributed to any changes in adjustment
4

o provides information about neuropsychological functioning prior to the occurrence of a
trauma or other event that results in a deficit.
Case history Study: a report or illustrative account concerning person or an event that was compiled
on the basis of case history data
o might shed light on how one individual’s personality and particular set of environmental
conditions combined to produce a successful world leader
o Groupthink: work on a social psychological phenomenon: contains rich case history material
on collective decision making that did not always result in the best decisions
Behavioral Observations
 monitoring the actions of others or oneself by visual or electronic means while recording quantitative
and/or qualitative information regarding those actions.
o often used as a diagnostic aid in various settings: inpatient facilities, behavioral research
laboratories, classrooms
o naturalistic observation: behavioral observation that takes place in a naturally occurring
setting (as opposed to a research laboratory) for the purpose of evaluation and information
gathering.
o in practice tends to be used most frequently by researchers in settings such as classrooms,
clinics, prisons, etc.
Role Play Tests
 Role play: acting an improvised or partially improvised part in a simulated situation.
 Role-play test: tool of assessment wherein assessees are directed to act as if they were in a particular
situation. Assessees are then evaluated with regard to their expressed thoughts, behaviors, abilities, et
Computer as Tools
 Local processing: on site computerized scoring, interpretation, or other conversion of raw test data;
contrast w/ CP and teleprocessing
 Central processing: computerized scoring, interpretation, or other conversion of raw data that is
physically transported from the same or other test sites; contrast w/ LP and teleprocessing
 Teleprocessing: computerized scoring, interpretation, or other conversion of raw test data sent over
telephone lines by modem from a test site to a central location for computer processing. contrast with
CP and LP
 Simple score report: a type of scoring report that provides only a listing of scores
 Extended scoring report: a type of scoring report that provides a listing of scores and statistical data.
 Interpretive report: a formal or official computer-generated account of test performance presented in
both numeric and narrative form and including an explanation of the findings;
o the three varieties of interpretive report are: descriptive, screening, consultive
 Interpretive report: a formal or official computer-generated account of test performance presented in
both numeric and narrative form and including an explanation of the findings;
o some contain relatively little interpretation and simply call attention to certain high, low, or
unusual scores that needed to be focused on
o consultative report: A type of interpretive report designed to provide expert and detailed
analysis of test data that mimics the work of an expert consultant
5
o
integrative report: a form of interpretive report of psychological assessment, usually
computer generated, in which data from behavioral, medical, administrative, and/or other
sources are integrated
CAPA
 computer assisted psychological assessment. (assistance to the test user not the test taker)
 enables test developers to create psychometrically sound tests using complex mathematical
procedures and calculations.
 enables test users the construction of tailor-made test with built-in scoring and interpretive
capabilities.
 Pros:
o test administrators have greater access to potential test users because of the global reach of
the internet.
o scoring and interpretation of test data tend to be quicker than for paper-and pencil tests
o costs associated with internet testing tend to be lower than costs associated with paper-andpencil tests
o the internet facilitates the testing of otherwise isolated populations, as well as people with
disabilities for whom getting to a test center might prove as a hardship
o greener: conserves paper, shipping materials etc.\
 Cons:
o test client integrity
 refers to the verification of the identity of the test taker when a test is administered
online
 also refers to the sometimes varying interests of the test taker vs that of the test
administrator. The test taker might have access to notes, aids, internet resources etc.
 internet testing is only testing, not assessment
CAT
 computerized adaptive testing: an interactive, computer administered test taking process wherein
items presented to the test taker are based in part on the test taker's performance on previous items
Other Tools
 DVD- how would you respond to the events that take place in the video
o sexual harassment in the workplace
o respond to various types of emergencies
 thermometers, biofeedback, etc
WHO, WHAT, WHY, HOW, AND WHERE?
Test Developer
 They are the one who create tests or other methods of assessment.
 They conceive, prepare, and develop tests. They also find a way to disseminate their tests, by
publishing them either commercially or through professional publications such as books or
periodicals
 American Educational Research Association, the American Psychological Association, and the
National Council on Measurement in Education (NCME)
6
o Standards for Educational and Psychological Testing covers issues related to test construction
and evaluation, test administration and use, and special applications of tests,
Test User
 They select or decide to take a specific test off the shelf and use it for some purpose. They may also
participate in other roles, e.g., as examiners or scorers.
 clinicians, counselors, school psychologists, human resources personnel, consumer psychologists,
experimental psychologists, and social psychologists
Test Taker
 Anyone who is the subject of an assessment
 May vary on a continuum with respect to numerous variables including:
o The amount of anxiety they experience & the degree to which the test anxiety might affect
the results
o The extent to which they understand & agree with the rationale of the assessment
o Their capacity and willingness to cooperate with the examiner or to comprehend written test
instructions
o The amount of physical pain or emotional distress they are experiencing
 The amount of physical discomfort brought on by not having had enough to eat, having had too
much to eat, or other physical conditions
 The extent to which they are alert and wide awake as opposed to nodding off
 The extent to which they are predisposed to agree or disagree when presented with stimulus
statements
 The extent to which they have received prior coaching
 The importance they may attribute to portraying themselves in a good (or bad) light
 The extent to which they are, for lack of a better term, “lucky” and can “beat the odds” on a multiplechoice achievement test (even though they may not have learned the subject matter).
 Psychological Autopsy -reconstruction of a deceased individual’s psychological profile on the basis
of archival records, artifacts, & interviews previously conducted with the deceased assesee
In What Types of Settings Are Assessments Conducted, and Why?
Educational Setting
 School ability tests - to help identify children who may have special needs
 Achievement test - evaluation of accomplishments or the degree of learning that has taken place,
usually with regard to an academic area
 Diagnostic test: a tool used to make a diagnosis, usually to identify areas of deficit to be targeted for
intervention
 Informal evaluation: A typically non systematic, relatively brief, and “off the record” assessment
leading to the formation of an opinion or attitude, conducted by any person in any way for any
reason, in an unofficial context and not subject to the same ethics or standards as evaluation by a
professional
Clinical Setting
 these tools are used to help screen for or diagnose behavior problems
7


The hallmark of testing in clinical settings is that the test or measurement technique is employed with
only one individual at a time.
group testing is used primarily for screening: identifying those individuals who require further
diagnostic evaluation
Counseling Settings
 schools,prisons, and governmental or privately owned institutions
 ultimate objective: the improvement of the assessee in terms of adjustment, productivity, or some
related variable
 Examples: measures of social and academic skills and measures of personality, interest, attitudes,
and values
Geriatric Settings
 quality of life: in psychological assesment, an evaluation of variables such as perceived
stress,loneliness, sources of satisfaction, personal values, quality of living conditions, and quality of
friendships and other social support
Business & Military Settings
 Sundry ways; most notably in decision making about the careers of personnel
 A wide range of achievement, aptitude, interest, motivational, and other tests may be employed in
the decision to hire as well as in related decisions regarding promotions, transfer, job satisfaction,
and eligibility for further training.
 Another application of psychological tests involves the engineering and design of products and
environments.
 Another application of psychological tests involves the engineering and design of products and
environments.
Governmental and organizational credentialing
 governmental licensing, certification, or general credentialing of professionals
 Board certification
HOW ARE ASSESSMENTS CONDUCTED?
How Are Assessments Conducted?
 Responsible test users have obligations before, during, and after a test or any measurement procedure
is administered.
 The test administrator (or examiner) must be familiar with the test materials and procedures and must
have at the test site all the materials needed to properly administer the test.
 Protocol: the form or sheet or booklet on which a test taker’s responses are entered
o term might also be used to refer to a description of a set of test- or assessment- related
procedures, as in the sentence “the examiner dutifully followed the complete protocol for the
stress interview”
 Test users have the responsibility of ensuring that the room in which the test will be conducted is
suitable and conducive to the testing.
 Rapport: working relationship between the examiner and the examinee
8


Responsible test users have obligations before, during, and after a test or any measurement procedure
is administered.
The test administrator (or examiner) must be familiar with the test materials and procedures and must
have at the test site all the materials needed to properly administer the test.
Assessment of People with Disabilities
 Define who requires alternate assessment, how such assessment are to be conducted and how
meaningful inferences are to be drawn from the data derived from such assessment
 Alternate assessment is typically accomplished by means of some accommodation made to the
assessee.
 Accommodation – adaptation of a test, procedure or situation or the substitution of one test for
another to make the assessment more suitable for an assessee with exceptional needs.
o Translate it into Braillee and administered in that form.
 Alternate assessment is an evaluative or diagnostic procedure or process that varies from the usual,
customary, or standardized way a measurement is derived, either by virtue of some special
accommodation made to the assessee or by means of alternative methods designed to measure the
same variable(s).
 Consider these four variables on which of many different types of accommodation should be
employed:
o The capabilities of the assessee
o The purpose of the assessment
o The meaning attached to test scores
o The capabilities of the assessor
WHERE TO GO FOR AUTHORITATIVE INFORMATION: REFERENCE SOURCES
Test Catalogues
 usually contain only a brief description of the test and seldom contain the kind of detailed technical
information that a prospective user might require
 Objective: to sell the test
Test Manuals
 Detailed information about the test
Reference Volumes
 one stop shopping, provides detailed information for each test listed, including test publisher, author,
purpose, intended test population and test administration time
Journal Articles
 may contain reviews of the test, updated or independent studies of its psychometric soundness, or
examples of how the instrument was used in either research or an applied context.
Online Databases
 most widely used bibliographic databases
 Educational Resources Information Center (ERIC)
 ERIC website at www.eric.ed.gov contains a wealth of resources and news about tests, testing, and
assessment.
 APA
 PsycINFO
 ClinPSYC
9




PsycSCAN
PsycARTICLES
Health and Psychosocial Instruments (HAPI)
PsycLAW
Consider the PROS and CONS
TYPES OF TEST
Individual Tests
 Those give to only one person at a time
Group Tests
 Administered to more than one person at a time by single examiner
Ability Tests
 Assess an individual's performance in different work related tasks or situations (work settings)
 ACHIEVEMENT TESTS – refers to previous learning
 APTITUDE/PROGNOSTIC – refers to the potential for learning or acquiring a specific skill
 INTELLIGENCE TESTS – refers to a person’s general potential to solve problems
Personality Tests
 refers to overt and covert dispositions
 OBJECTIVE/STRUCTURED TESTS – usually self-report, require the subject to choose between
two or more alternative responses
 PROJECTIVE/UNSTRUCTURED TESTS – refers to all possible uses, applications and underlying
concepts of psychological and educational test
10
TABLE OF SPECIFICATIONS
11
12
13
14
Psychometrician
A Psychometrician is a professional who has been registered and issued a valid Certificate of
Registration and a valid Professional ID Card as such by the Professional Regulatory Board of Psychology
and the Professional Regulation Commission to practice Psychometrics.
Psychometrics is the branch of psychology that deals with the development, administration, and
interpretation of quantitative tests for the measurement of psychological variables such as intelligence,
aptitude, and personality traits
Functions
 Administering &scoring objective and structured personality tests;
 Interpreting the results of these tests and preparing a written report on these results;
 Conducting preparatory intake interviews for psychological intervention sessions;
 Test design and construction: developing the table of specifications, item writing and item analysis;
 Test validation & standardization: developing norm sampling plans; conducting item tryout data
analysis; completing analysis and scale development
 Writing the Technical Manual
 Test Research and Statistical Studies.
Skills and Competencies
 Discipline, Knowledge, Research and Scientific Foundation
 Framing, Measuring, Planning;
 Constructing and Calibrating Test Items;
 Statistical Procedures, Tools and Computer Applications
 Data Management, Analysis, and Reporting
 Interviewing and Relational Skills
 Administration of different types of psychological tests using innovative delivery platforms; scoring,
profiling and interpreting the results thereof;
 Assessment and Evaluation
 Writing a Psychological Report
 Professional, Legal and Ethical Practice
 Attention to details in the pursuit of Accuracy
 Oral and Written Communication
 Independence and Collaborative Cooperation
Basic Educational Requirements
To become a Psychometrician, you need to have a Bachelor’s Degree in Psychology and pass the
licensure examination for Psychometricians.
Formal learning as a psychometrician is only the beginning. The internship and strong mentoring
relationship with an experienced psychometrician is critical. There is a big jump between the theory of
psychometrics and the art and science of doing it in the real world.
Cost of Education
A Bachelor’s degree in Psychology is offered in at least 286 colleges and universities in the
Philippines. The tuition fee normally ranges from PHP 5,000.00 to PHP 20,000 per semester in State
Colleges and Universities, and from PHP 25,000 to PHP 65,000 per semester in private schools.
15
Employment Opportunities
Psychometrics is a specialized field and there is a shortage of licensed psychometricians, more so
now with regulatory laws, the push for educational accountability and the demand for quality assurance in
testing programs.
There is a growing demand for Psychometricians in hospitals and mental health institutions as part of a
multidisciplinary Psycho-diagnostic Team; in schools as part of the Testing, Admissions and/or Guidance
team; and in business and industry as part of the HR Management team. Psychometricians are needed too in
Psychological Test Centers, OFW clinics, in the military (PNP, AFP, PCG) and in various government
agencies (DSWD, DOH, NCMH, DDB, NBI) and the Judiciary under the supervision of the Psychologists.
THE SCIENCE OF PSYCHOLOGICAL MEASUREMENT: STATISTICS REFRESHER
Scale of Measurement
1. Nominal Scales - involve classification or categorization based on one or more distinguishing
characteristics, where all things measured must be placed into mutually exclusive and exhaustive
categories.
2. Ordinal Scales - permit classification and rank ordering on some characteristic
3. Interval Scales - contain equal intervals between numbers; aach unit on the scale is exactly equal to
any other unit on the scale; contain no absolute zero point.
4. Ratio Scale - has a true zero point
Measurement Scales in Psychology
 Ordinal level of measurement is most frequently used in psychology.
o Intelligence, aptitude, and personality test scores
 “Most psychological and educational scales approximate interval equality fairly well,” (Kerlinger,
1973)
Describing Data
Accomplishment 1
 Lorem ipsum dolor sit amet, consectetur adipiscing elit
 Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Accomplishment 2
 Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea
commodo consequat.
Frequency Distributions
Grouped Frequency Distribution
 State the procedures
Ungrouped Frequency Distribution
 State the nature and how will it be treated
Graph
 a diagram or chart composed of lines, points, bars, or other symbols that describe and
illustrate data
Kinds:
 Histogram
16



Bar graph
Frequency Polygon
Shapes of the Frequency Distributions
Measures of Central Tendency
Measures of Central Tendency
 A statistic that indicates the average or midmost score between the extreme scores in a
distribution
Commonly used MCT:
 The arithmetic mean
 The median
 The mode
Percentiles
A single test score means more if one relates it to other test scores. A distribution of scores
summarizes the scores for a group of individuals. In testing, there are many ways to record a
distribution of scores.
 Indicate the location of a score in a distribution
 Range from 1 to 99
 Example:
o Pearl scored 59th percentile on an exam.
o This means that Pearl scored better than (approximately) 59% of the people on the exam.
 Example 2:
o Margie scored at the 85th percentile on a standardized test (such as the SAT).
o As she scored 85th percentile, this indicates that Margie scored better than 85% of the
people on the exam.
 Indicate the percentage of scores that a given value is higher or greater than.
 3rd percentile: scored better than 3% of examinees.
 40th percentile: scored better than 40% of the examinees



Can be thought of as dividing scores into two separate groups
3rd percentile: 3% scored below this point, 97% scored above
40th percentile: 40% scored below this point, 60% scored above



Certain percentiles go by other names as well
25th percentile: scored better than 25% of the examinees. Also known as Q1 or first quartile
50th percentile: Also known as Q2 or second quartile; also equal to the median as it splits the
distribution exactly in half
75th percentile: Also known as Q3 or third quartile




The first decile or the 10th percentile separates the bottom 10% of examinees from the top
90%.
The second decile or the 20th percentile separates the bottom 20% of examinees from the top
80%.
And so on...
17
Decile




D1 = first decile (10th percentile)
D2 = second decile (20th percentile)
D3 = third decile (30th percentile)
And so on….until we get to D9 ninth decile (90th percentile)
18
Measures of Variability
Variability
 An indication of how scores in a distribution are scattered or dispersed.
Measures of Variability
 Statistics that describe the amount of variation in a distribution
 Some measures of variability include the range, the interquartile range, the semi-interquartile
range, the average deviation, the standard deviation, and the variance.
Range
 The difference between the highest and lowest values in the set
Quartile and Quarter
 Quartile: the dividing points between the four quarters in the distribution refers to a specific
point
 Q1 , Q2 , and Q3
 Quarter: refers to an interval
 An individual score may, for example, fall at the third quartile or in the third quarter (but not
“in” the third quartile or “at” the third quarter).
Interquartile range
 Interquartile range = difference between Q1 and Q3
o Step 1. Put the Numbers in order.
2, 4, 5, 6, 7, 9, 10
o Step 2. Find the Median
(2, 4, 5) 6 (7, 9, 10)
o Step 3. Find Q1 (median of the lower half of the data) and Q3 (median of the upper
half of the data)
(2, 4, 5) 6 (7,9, 10) Q1=4 Q3=9
o Step 4. Subtract Q1 from Q3
9-4 = 5
Semi-Interquartile Range (SIR)
 Is equal to the interquartile range divided by 2.
 (Or) one half the difference between the 75th percentile [often called (Q3)] and the 25th
percentile (Q1).
 Knowledge of the relative distances of Q1 and Q3 from Q2 (the median) provides the
seasoned test interpreter with immediate information as to the shape of the distribution of
scores.
 In a perfectly symmetrical distribution, Q1 and Q3 will be exactly the same distance from the
median.
 If these distances are unequal then there is a lack of symmetry. This lack of symmetry is
referred to as skewness.
Average Deviation
 What is the formula?
 All the deviation scores are summed and the divided by the total number of scores ( n )
Variance
 Equal to the arithmetic mean of the squares of the differences between the scores in a
distribution and their mean.
 State the procedures/steps in determining variance..
Standard Deviation
19


Measure of variability equal to the square root of the average squared deviations about the
mean
State the procedures/steps in determining SD.
Skewness
Skewness
 The nature and extent to which symmetry is absent
 Refers to an asymmetrical distribution with data points that do not cluster symmetrically
around a mean; some distributions may have scores or data points that cluster toward the
lower end or the higher end of the distribution.
 Is directly related to measure of central tendency.
Positive Skew
 When relatively few of the scores fall at the high end of the distribution.
 Positively skewed examination results may indicate that the test was too difficult
Negative Skew
 When relatively few of the scores fall at the low end of the distribution.
 Negatively skewed examination results may indicate that the test was too easy
Kurtosis
Kurtosis
 Refer to the steepness of a distribution in its center
 It is derived from the Greek word referring to “peakedness.”
 The height of the distribution provides one with a lot of information about how data points
are clustered. The more data points or scores are clustered around a mean, the more peaked
the distribution. The further scores are dispersed from the mean, the flatter the distribution.
 Three general shapes of distributions are mesokurtic (normal curve), leptokurtic (tall and thin
and platykurtic (flat and wide)
20
The Normal Curve
Normal Curve
 a bell-shaped, smooth, mathematically defined curve that is highest at its center.
The Area Under the Normal Curve
21
The Area Under the Normal Curve
 50% of the scores occur above the mean and 50% of the scores occur below the mean.
 Approximately 34% of all scores occur between the mean and 1 standard deviation above the
mean.
 Approximately 34% of all scores occur between the mean and 1 standard deviation below the
mean.
 Approximately 68% of all scores occur between the mean and (-/+) 1 standard deviation.
 Approximately 95% of all scores occur between the mean and (-/+) 2 standard deviations.
Standard Scores
 A raw score that has been converted from one scale to another scale (has some arbitrarily set mean
and standard deviation).
 Different systems for standard scores exist, each unique in terms of its respective mean and standard
deviations.
Z score
 Zero plus or minus one scale
 Results from the conversion of a raw score into a number indicating how many standard deviation
units the raw score is below or above the mean of the distribution.
 Especially useful for showing exactly where a particular score falls on the normal curve
 How to change a raw score to a z-score:
o
T scores
 Devised by W. A. McCall (1922, 1939) and named a T score in honor of his professor E. L.
Thorndike
 Composed of a scale that ranges from 5 standard deviations below the mean to 5 standard deviations
above the mean.
 Fifty plus or minus ten scale
 Advantage: none of the scores is negative as compared to z-scores
Z-scores vs. T scores
 When to use z-scores?
o Has a simple size above 30
o Standard deviation is known
 When to use T scores?
o Has a sample size below 30,
o Has an unknown population standard deviation.
22
Other standards scores
 Stanine = contraction of the words standard and nine
 are different from other standard scores in that they take on whole values from 1 to 9, which
represent a range of performance that is half of a standard deviation in width
23
Correlation and Inference
The Concept of Correlation
 The degree and direction of correspondence between two things
 A coefficient of correlation ( r ) expresses a linear relationship between two (and only two)
variables, usually continuous in nature. It reflects the degree of concomitant variation
between variable X and variable Y.
The Pearson r
 Devised by Karl Pearson
 r can be the statistical tool of choice when the relationship between the variables is linear and
when the two variables being correlated are continuous
 Review: 2 ways to determine the r
 Common formula
The Spearman Rho
 Rank-order correlation coefficient , a rank-difference correlation coefficient
 Developed by Charles Spearman, a British psychologist
 this coefficient of correlation is frequently used when the sample size is small (below 30)
Graphic Representations of Correlation
 A scatterplot is a simple graphing of the coordinate points for values of the X -variable (placed
along the graph’s horizontal axis) and the Y -variable (placed along the graph’s vertical axis).
24
Meta-analysis
 May be defined as a family of techniques used to statistically combine information across
studies to produce single estimates of the data under study
o The estimates derived, referred to as effect size , may take several different forms.
 Key advantage: more weight can be given to studies that have larger numbers of subjects
 Some advantages are:
(1) meta-analyses can be replicated; (2) the conclusions of meta-analyses tend to be more
reliable and precise than the conclusions from single studies; (3) there is more focus on effect
size rather than statistical significance alone; and (4) meta-analysis promotes evidence-based
practice, which may be defined as professional practice that is based on clinical and research
findings