Chapter 2

Psychological Research Methods and Statistics

Section 1

What is Research?

Jane Goodall

• Observed chimpanzees in Tanzania, Africa for more than 30 years

• she used the research method of naturalistic observation

• Collect information like most people do in everyday life-only more carefully and more systematically

Pre-Research Decisions

• Must ask a specific question about a limited topic or hypothesis

• The method or research depends on the research topic

• It does not matter what approach the data is collected, but decisions need to be made ahead of time

Samples

• A sample is the small group of participants, out of the total number available, that a researcher studies

Methods of Research

• Naturalistic observation- research method in which the psychologist observes the subject in a natural setting without interfering

• Case study- research method that involves an intensive investigation of one or more participants

Methods of Research

• Surveys- research method in which information is obtained by asking many individuals a fixed set of questions

• Longitudinal study- research method in which data are collected about a group of participants over a number of years to access how certain characteristics change or remain the same during development.

Methods of Research

• Cross-sectional study- research method in which data are collected from groups of participants of different ages and compared so that conclusions can be drawn about differences due to age.

• Correlation-the measure of a relationship between two variables or sets of data

Experiments

• Hypothesis- an educated guess about the relationship between two variables

• Variable- any factor that is capable of change• Experimental group- the group to which an

independent variable is applied• Control group- the group that is treated in the

same way as the experimental group except that the experimental treatment (the independent variable is not applied.

Ethical Issues

• Ethics- the methods of conduct or standards, for proper and responsible behavior

• Using animals in research has become an issue in recent years

Section 2

Problems and Solutions in Research

Self-fulfilling Prophecy

• Is a situation in which a researcher’s expectations influence that person’s own behavior, and thereby influence the participants behavior.

Avoiding a Self-fulfilling Prophecy

• Single-blind experiment- is an experiment in which the participants are unaware of which participants received the treatment

• Double-blind experiment- is an experiment in which neither the experimenter nor the participants know which participants received which treatment

• By conducting this type of experiment the researcher can remain unbiased.

The Milgram Experiment

• Stanley Milgram wanted to determine whether participants would administer painful shocks to others because an authority figure instructed them to do so

• He gathered 1000 participants

• The volunteers were paired with learners

• The volunteer would shock the learner when the learner made a mistake

The Milgram Experiment

• The volunteers were told that with each mistake, the electrical shock would become stronger

• The volunteers did not realize the shocks were fake

• 65% of the volunteers pushed the shock button until it reached maximum severity

• Proved that ordinary individuals could easily inflict pain if orders were given by a respected authority

The Milgram Experiment

• Was an excellent example of a single-blind experiment

• Swarthmore College conducted the same study

• 88% of undergraduates administered the highest level of shock

The Placebo Effect

• Is a change in a participant’s illness or behavior that results from a belief that the treatment will have an effect rather than from the actual treatment

• Psychiatric patients in two study groups were given a drug, after a six-week period the groups were evaluated

The Placebo Effect

• 53% to 80% reported they benefited from the drugs

• The drugs administered were placebos• The people reacted to their own

expectations of how the drug given would affect them.

• Neither the researchers or the patients new they were placebos until after the experiment

Section 3

Statistical Evaluation

Statistics

• The branch of mathematics concerned with summarizing and making meaningful inferences from collections of data

• Descriptive Statistics- the listing and summarizing of data in a practical, efficient way

Distributions of Data

• Frequency distribution- an arrangement of data that indicates how often a particular score or observation occurs

• Find the percentage– Divide the frequency of the participants within

a category by the total number of participants and multiplying times 100.

Distributions of Data

• Histograms- similar to bar graphs, except they show frequency distribution by means of rectangles whose widths represent class intervals and whose areas are proportionate to the corresponding frequencies

Distributions of Data

• Frequency polygons– Are useful because they provide a clear picture of the

data distribution

• Normal curve (bell-shaped curve)– a graph of frequency distribution shaped like a

symmetrical, bell-shaped curve; a graph normally distributed data

– Curve is symmetrical – Can divide the curve into sections to determine what

percentage falls into each area

Measures of Central Tendency

• Is a number that describes something about the “average” score of a distribution

• Mode- the most frequent score• Bimodal- distributions with two modes• Median- is the middle score (least to most)• Mean- usually referred to as the average

and commonly used measure of central tendency (add all scores and divide by total number of scores)

Measures of Variability

• Variability- a measure of difference, or spread of data– Range- subtract the lowest score from the

highest score and add 1.– Standard deviation- a measure of variability

that describes an average distance of every score from the mean.

• Scores above the mean are positive, below are negative

• Larger the SD, the more spread out the scores

Correlation coefficient

• Describes the direction and strength of the relationship between two sets of variables– (+) as one variable increases the second

variable increases– (-) as one variable increases, the other

variable decreases– Scatterplot- is a graph of participants’ scores

on the two variables, and it demonstrates the direction of the relationship between them

Inferential Statistics

• Numerical methods used to determine whether research data support a hypothesis or whether results were due to chance

• Probability and Chance

• Statistical significance

Source:

• Kasschau, Richard, A. Understanding Psychology. McGraw-Hill, Glencoe, New York, New York, 2008.