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)