General Psychology
Research Methods in Psychology
Dr. Christopher Gade
UC Berkeley Extension
Why Methods and Statistics?
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Despite psychology majors’ (and some faculty’s) aversion to statistics,
the field of psychology was built on a firm understanding of statistical
theory and practice
Why?
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Psychology is a social science, not an exact science
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Developmental ideas example
Name example
Psychology has a history of and current issues with pseudo-scientific
approaches to the field, so we have to inoculate ourselves from this
approach as much as possible
Research Methods in Psychology
Basic Goal of Statistics
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Psychologists are interested in studying
topics that we can apply to everyone in a
population
HOWEVER, we often CANNOT look directly
at a population, and most effects we study
DO NOT apply to everyone
To adjust, we collect information on
samples and then use the information that
we obtain from them to make inferences
about a population
Statistical comprehension is a MUST for us
to accomplish this goal
Research Methods in Psychology
Important Tests In Statistics
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Experimental (Comparison) Tests
• Determining effects of treatments or differences
between groups
• Independent/Dependent Variables
• Treatment/Control Groups
• Group comparisons across a variable (usually comparing
averages) can be of 2, 3, or even more groups
Research Methods in Psychology
Important Tests in Statistics (continued)
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Correlational Test
• Correlation measures (r)
• Measures two or more
characteristics of variables
within an individual
• Strength/direction of
relationships (+, -, 0)
• Predictor/criterion variables
Research Methods in Psychology
What Forms Can These Variables Take?
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Nominal
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Ordinal
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Variables separated by rank ordered groups
If numbers are indicated, they are being used to indicate rank
Examples: Age Groups, Letter Grades in a Class
Interval
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Variables separated by groups
If numbers are indicated, they are being used as labels
Examples: Favorite Ice Cream Flavor, Gender
Identical intervals mean equivalent differences
Examples: IQ Scores, Temperature in Fahrenheit
Ratio
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Identical ratios mean equal proportions
True zero
Examples: Age, Income
How We Compare Groups In Experiments
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To compare 2 or more groups, you
need two things:
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A measure of central tendency
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A measure of variability
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Mean – arithmetic average
Median – middle score
Mode – most common
Standard deviation – individuals
Standard errors - groups
These give you Z, z, t, T, F, Χ,∆, or
other statistical scores that you use
What We Do With Sample Data
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Guess at the strength of a relationship between variables
Indicate the expected impact that a change in one variable would have
on another one
Guess at the certainty that a manipulation had an effect
Guess at the magnitude of the effect that a manipulation can have on
an individual/group
NOTE: remember, psychology is a social science, we can only discuss
general trends and suggested relationships, not absolute certainties in
this science
Research Methods in Psychology
Moving On
Now that we’ve defined psychology, discussed what people can
look at in the field, and covered how they examine their topics,
we can get into the specific branches of psychology
• In our next module, we’ll start where psychologists have started
for over a century—with the link between biology and the
processes of the mind
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Research Methods in Psychology