Research and Statistics in Psychology

Wadsworth, a division of Thomson Learning

What Makes Psychology a Science? The methods it uses to ask its questions

about behavior and mental processes. The belief that results obtained from its

scientific inquiry should be able to be repeated.

The Scientific Method Theory-Long-standing explanation for a

behavioral phenomenon, based on prior observations.

Hypothesis-prediction of what will happen in the experiment

Gather Data-Taking data from a sample regarding your question.

Data analysis-Determining what the data mean.

Communicate Results-presenting at a conference or publishing in a journal

Common Research Methods In Psychology Case Study Survey Naturalistic

Observation Participant

Observation

Test Methods Correlation Experimental

Method

Case Study

Popularized by Sigmund Freud Detailed history of a single individual Usually used when an individual

demonstrates a rare disorder or symptomatology

It is limited in that the findings cannot be generalized to a larger population, but it may provide direction for further research.

Survey A common form of research that allows the

gathering of large amounts of data in very large populations.

During the administration of a survey, an investigator must take care to obtain a representative sample of their population.

Questions must be clear, non-biased, and appropriately formatted to obtain meaningful data.

Survey

Surveys may be conducted in person, on the phone, on the computer, or through the mail.

Cannot draw causal conclusions from the results.

Naturalistic Observation

Formal record of observed events in a natural setting. The scientist making the observations must be unobserved by the subject.

What a scientist gains by placing the subject in their natural setting they may lose by losing control over extraneous variables.

The scientist doing naturalistic observation must also be very careful to not let their own beliefs about what should happen in the naturalistic setting affect the way they “see” the events unfolding.

Test Method

Standardized tests are administered to a population. (Example: the SAT’s and the ACT’s are standardized tests)

Tests must have high reliability (measures the same thing every time) and high validity (measures what you say it does) for the data obtained from them to be meaningful.

Correlation Determines the relationship between two

variables. The relationship is defined by a number

from -1.0 to +1.0 The closer the number is to either -1.0 or

+1.0 the stronger the relationship The (-) and (+) identify the direction of the

relationship. A (-) means that as one variable increases the other decreases. A (+) means that as one variable increases the other increases as well.

Correlations Continued

Correlations are generally viewed using a scatterplot.

Correlations never allow you to draw causal conclusions. One reason for this, is that there may be a third variable influencing both of the variables used in your correlation.

Experimental Method

This method can provide cause-and-effect conclusions.

This method involves the manipulation of an independent variable to determine how it affects a dependent variable.• Independent-the variable that is manipulated• Dependent-the variable that is measured to

determine the effect of the independent variable

Experimental Method

This method makes use of control groups and experimental groups.• Control Group-a group that receives the

identical treatment as the experimental group except for the independent variable

• Experimental Group-a group that receives the manipulation of the independent variable

Descriptive Statistics

Used to summarize the data gathered in an experiment

Measures of central tendency• Mean-the arithmetic average• Median-the number that divides the ordered

scores in half• Mode-the most frequently occurring score

Descriptive Statistics

Measures of Variance• Variance-a measure that reflects how similar all

of the numbers in your group are• Range-measure of variability that is obtained

by subtracting the smallest score from the largest

• Standard Deviation-Square root of the variance important in determining the normal distribution

Normal Distributions A bell-shaped distribution of the scores of

an experiment where half of the scores fall above the mean and half of the scores fall below the mean

The peak of the curve is the mean Specific percentages of scores will fall

within set standard deviations from the mean• example: 68% of the scores will fall within one

standard deviation from the mean

Testing for Significance

A statistical comparison of a control group and an experimental group to determine if their measures on the dependent variable are significantly different.

If they are, it means the scientist can say with 95% confidence that the two groups are different because of the independent variable.