A look at psychological research
General principles
• The specious attraction of anecdotes
• The concern for precise measurement• Operational definitions – definitions which
specify the procedure used to measure something
• Also, a way to give a study’s focus of concern a numerical value
• How do you measure anger, love, intelligence?
Population samples
• Population – the entire
group of individuals of
interest
Sample – a small group
chosen from the popu-
lation
Types of samples
• Convenience – a sample chosen because of its availability
• Far from ideal, but very common
“The study of 20 year old college sophomores.” ?
• Representative – a sample which closely mirrors the population in all characteristics likely to affect the results
• Ideal but hard to find
Samples cont.
• Random samples – a sample in which every individual in the population has an equal chance of being selected.
• Hard to get, but many benefits
• Cross-cultural samples – samples which include groups from at least two separate cultures
• Discuss concerns in Interpretations
Research designs
• Naturalistic observations• A careful examination ofan individual’s or animal’sbehavior in more or less natural conditions
No manipulation, just observationOften the first step in generating hypothesis’
Case histories
• A thorough description of a
person or small group of
people with unusual or
noteworthy qualities
Another source of hypothesis’
Just a super-sized anecdote?
surveys
• A study of the prevalence of certain beliefs, behaviors, or attitudes based upon people’s responses to specific questions
• Many problems:
sampling
nonchalance
the questions
bias
correlations
• A measure of the relationship between two variables
• Variable – a measurable item that can vary in magnitude
• Correlational study – a procedure in which the investigator measures the relationship between two variables without controlling either one
Correlationsexamples
• Between class attendance and final grade• Between hours worked and $ earned• Between smiles given and smiles received
• Between miles run/week and 5k time• Between hours on internet and final grade• Between exercise sessions and weight
• Between hair color and grade point average
Correlations graphicexamples
The correlation coefficient
• R = the mathematical relationship between two variables, ranging from -1 to 1
• Positive correlations approach 1• Negative correlations approach -1• A R of 0 means that there is no relationship
between the two variables• Look to R’s absolute value when assessing
its strength
Illusory correlations
• An apparent relationship based upon casual observations of unrelated or weakly related events
• Do people really get
wild under a full moon?
Does the weather affect
arthritis symptoms?
Correlations and causation
• No matter how it might seem, correlations do not tell us about cause and effect
• We never really know if changes in one variable affects the other, or
• If a third, lurking, variable controls them both.
• Correlations help us predict but not explain or control behavior or experience.
experiments
experiments
• A study in which the investigator manipulates at least one variable while measuring at least one other variable
• By adjusting one variable or factor, while keeping all other factors constant, we can determine if that factor causes changes in the other(s)
More definitions:variables
• Independent variable – the variable which is manipulated, or adjusted, by the investigator
• Dependent variable – the variable which is measured by the investigator to determine the effects of the independent variable
• Thoughtfully quantified through the operational definition
Even more:groups
• Experimental group – receives the treatment (independent variable) that the experiment was designed to test
• Control group – handled exactly the same as the experimental group except for the independent variable
• Control groups usually receive a placebo
Hazards to be prepared for
• Biased groups• to make sure that the experimental and control
groups are as similar as possible, before being introduced to the independent variable we use random assignment
• every participant must have an equal chance of being placed in either the experimental or the control group
more hazards
• Even unconsciously, investigators want to see their hypothesis confirmed and unintentionally might distort the results
• Also, the experiment’s participants might try to help prove the hypothesis
Solution – Double blind – a procedure in which both the observer and the participant are unaware of which participants received which treatment and the experiment’s goals
review
• Hypothesis
• Select Method & Operational Definition
• Acquire Sample
• Random Assignment of groups
• Run experiment (double blind)
• Collect and analyze results (data)