CHAPTER 11
Intrasubject
Research:
Small-N Designs
Copyright, 2005, Prentice Hall, Sarafino
What is an Intrasubject
Design?
• An intrasubject, sometimes called a
small-N design, design refers to research:
– That manipulates an independent variable
– That is carried out on only one, or at the
most, a few participants.
– Where the participant is measured over
time.
– Where individual data for each participant is
presented – usually in a graphical form.
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Overt Behavior
• Overt behaviors are those that can be viewed or
directly assessed.
• There are 2 types of overt behavior:
– Verbal (use of language, e.g., words)
– Motor (body movement, e.g., running speed).
• Common measures associated with overt
behavior include:
– Performance speed
– Trials
– Reaction time
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Covert Behavior
• Covert behaviors are those that are not
directly observable.
– Some examples include feelings, current
physical states, and attitudes.
– If we can’t directly observe covert behavior
then how do we measure it?
• We can measure covert behaviors directly with
machines (e.g., heart rate monitor) or indirectly
(e.g., self-reports).
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Direct and Indirect Measures of
Covert Behavior
• Direct techniques can include:
– EEG (cortical brain activity)
– GSR (skin conductivity)
– PET and MRI (brain imaging).
• Indirect techniques can include:
– Surveys
– Questionnaires
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Surveys and Questionnaires
• Surveys and questionnaires are important
methods psychologists use to gather information
about covert behavior.
• They generally include some of the following
characteristics:
– Closed-ended items (participants are restricted to a
set of fixed responses, e.g., true/false, multiple choice
questions.)
– Open-ended items (participants are free from
response restriction, e.g., What do you think about
serial killers?).
Copyright, 2005, Prentice Hall, Sarafino
Types of Closed-Ended Items
• Closed-ended items are generally superior to
open-ended items because they are much
easier to score (remember this when you do
your Honors Thesis).
• There are many useful ways to present closeended items to participants each with their own
set of pros and cons:
–
–
–
–
Point scales
Likert scales
Segmented rating scales
Numerical rating scales
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Composing a Survey
• Before you start, check the thousands of
published psychological survey and tests
to see if one already exists on your topic.
– If not, then you need to create one. The
following steps will help you:
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Composing a Survey
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Describe, in detail, your measure and refer to this description often.
Decide on who you will measure. Why?
Design items to gather demographic data.
Design numerous items only on the topic you are interested in – do not
try to measure everything.
Rework your items – e.g., make them as simple and straightforward as
possible. Avoid jargon, technical terms, negative wording, and doublebarreled items.
If using closed-ended items, be sure your response sets cover the
complete range of possible answers in equal increments. Why? And be
sure you response sets match the question. Why?
Decide on the statistics you are likely to use.
Pretest the survey on a group of people who will not be in your actual
study. Tell them you want constructive criticism.
Revise the test and make it look professional.
Now the fun part begins – giving the survey and deciding if your survey is
reliable and valid. This comes in later chapters.
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Other Types of Data: Remnant
• Remnant data refers to the use of existing
remains, products, or evidence of behavior
to infer or explain past events.
• Some examples include:
– Physical Traces
•
E.g., Graffiti, garbage.
– Archival Data
•
E.g., birth weights and rates, weather reports
and crime.
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How to Identify Pseudoscience?
• The “Trappings” of Science
– Pseudoscience tries to be like real science.
– Pseudoscience makes predictions about
phenomenon, but rarely tests them.
• Data is Often Based on Testimonials
– Data like this can be easily manipulated.
• Evasion of Disproof
– Explanations given by the pseudoscience to account
for data that disprove the pseudoscience are
difficult/impossible to test (e.g., the phenomenon can’t
be measure by conventional means)
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Naturally Occurring Behavior
• Sometimes psychologists want to study ongoing
or naturally occurring behavior.
• This is unique because researchers not only
have to be concerned about what they are
observing, but also when and where the
behavioral observations will be made.
• To deal with this, psychologists often employ:
– Time sampling technique
•
Taking samples of behavior only at certain times.
– Event or Situation sampling technique
•
Taking samples only in a predetermined situation.
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Types of Data
•
The are two main categories of data:
1. Quantitative
•
Is numerical or can easily be converted to
numerical form.
2. Qualitative
•
Usually narrative in nature and difficult if not
impossible to convert to numerical.
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Scales of Measurement
•
•
Once you have determined the type of data you
will generate, you now need to coordinate this
with statistics procedures.
The first step in doing this is to determine your
data’s “scale of measurement”.
– There are 4 Different Scales of Measurement
1.
2.
3.
4.
Nominal
Ordinal
Interval
Ratio
Let’s consider each one.
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Nominal Scale
• Most basic level of measurement.
• Numbers represent simple qualitative
differences in your variables.
– E.g., 1 = group_1; 2 = group_2, etc.
• Numbers are not intended for numerical
calculations, but to classify data.
• General rule: Similar objects or events are
assigned similar numbers, and different objects
get different numbers.
• Statistical procedures:
– Frequency counts; Chi-Square.
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Goals of Scientific Research
•
There are 4 main goals of scientific
research:
1.
2.
3.
4.
Description
Prediction
Understanding
Application
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Research Strategies
•
There are 4 main research strategies
used in psychological research and
covered in detail in the remainder of the
text:
1.
2.
3.
4.
The Experimental Strategy
The Quasi-experimental Strategy
The Correlation Strategy
The Descriptive Strategy
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