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PSYCH 9A
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Lecture 2

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Cognitive Sciences

PSYCH 9A

Thomas Michael D' Zmura

Winter

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CHAPTER 1: RESEARCH METHODS
Making Observations
• Look for patterns within our observations variables- any characteristic whose values
can change
Defining the Question
• Guided by questions we hope to address through our observations
• Formulate the question in a way that leaves no doubt about how we’re going to link the
question to the evidence we collect
• Testable hypothesis- a prediction that has been formulated specifically enough so that it
is clear what observations would confirm the prediction and what observations would
challenge it
o Testability guaranteed by ensuring the hypothesis is falsifiable
• To address a question, we need to develop an operational definition- a definition that
translates the variable we want to assess into a specific procedure or measurement
• Dependent variable- variable that is measured or recorded in an experiment;
independent variable- variable that the experimenter manipulates as a basis for making
predictions about the dependent variable
Systematically Collecting Data
• Memories are often selective; confirmation bias
• Anecdotal evidence (evidence that involved 1-2 cases) not used to draw conclusions
Defining the Sample
• Psychologists often want their conclusions to apply to a particular population- the entire
group about which the investigator wants to draw conclusions
o Investigators study only a sample- the subset of a population that the investigator
studies in order to learn about the population at large
• Because each person is different from one another random sampling- a procedure in
which every member of the population has an equal chance of being picked to
participate in a study
o Other approaches:
If want to examine how diverse population is maximum variation
sampling (deliberately seek out unusual cases)
Case study- an intensive study of one person
• H.M. – most studied man in history, suffered memory deficits
• Phineas Gage – frontal lobe damage
Assessing External Validity
• If we want our study to reflect the broader world, we need to ensure its external validity-
the degree to which a study’s participants, stimuli, and procedures adequately reflect the
world as it actually is
o Sample of people in study must be representative of the broader population
Monitoring Demand Characteristics
• Demand characteristics- the cues in a study that might tell a research participant what
behaviors are expected or desirable in that setting
• To minimize a study’s demand characteristics:
o 1. Try to phrase questions as neutrally as possible
o 2. Treat all study participants alike
Double-blind design- the technique of assigning participants to
experimental conditions while keeping both the participants and the
researchers unaware of who is assigned to which group Working With Data
• Analysis involves two parts:
o 1. Descriptive statistics- allow a researcher to characterize a data pattern; include
measures of central tendency and of variability
o 2. Inferential statistics- allow a researcher to draw further claims from a data
pattern, including claims about whether the pattern observed in the sample is
likely to be observed in other samples
Descriptive Statistics
• Means and Variability
o Measure of central tendency
Mean- calculating sum of all observations, then dividing by number of
observations
Median- measure of central tendency taken by putting the data values in
order and finding the value that divides the distribution in half
o Variability- the degree to which scores in a frequency distribution depart from the
central value
Standard deviation- measure of the variability of a data set, calculated as
the square root of the variance (V)
• Correlations
o Correlation- tendency of two variables to change together; if one goes up as the
other goes up, positive correlation. If one goes down as the other goes down,
negative correlation
o Correlation coefficient (r)- a number that expresses both the size and the
direction of a positive correlation, varying from +1.00 (perfect positive correlation)
to -1.00
Always calculated on pairs of observations
• Correlations and Reliability
o Reliability- the degree of consistency with which a test measures a trait or

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