Chapter 6: Foundations: Methods and Approaches

experiment

experiment

is an investigation seeking to understand relations of cause and effect.

independent variable

The manipulated variable is called the

dependent variable

what is measured.

Representativeness

is the degree to which a sample reflects the diverse characteristics of the population that is being studied.

Random sampling

is a way of ensuring maximum representativeness

bias of selection

from a specific real area occurs when people are selected in a physical space.

Self-selection bias

occurs when the people being studied have some control over whether or not to participate.

Pre-screening or advertising bias

occurs often in medical research; how volunteers are screened or where advertising is placed might skew the sample.

Healthy user bias

occurs when the study population tends to be in better shape than the general population.

Single-blind

means that the subjects do not know whether they are in the control or experimental group.

Double-blind

studies are designed so that the experimenter does not inadvertently change the responses of the subject, such as by using a different tone of voice with members of the control group than with the experimental group.

Correlational research

involves assessing the degree of association between two or more variables or characteristics of interest that occur naturally.

surveys

One way to gather information for correlational studies is through

Clinical research

often takes the form of case studies.

Case studies

are intensive psychological studies of single individuals.

conceptual definition

is the theory or issue being studied

operational definition

refers to the way in which that theory or issue will be directly observed or measured in the study.

Internal validity

is the certainty with which the results of an experiment can be attributed to the manipulation of the independent variable rather than to some other, confounding variable.

External validity

is the extent to which the findings of a study can be generalized to other contexts in the “real world.”

inter-rater reliability

the degree to which different raters agree on their observations of the same data.

Descriptive statistics

summarize data

inferential statistics

allow researchers to test hypotheses about data and determine how confident they can be in their inferences about the data.

mean

is the arithmetic average of a set of numbers.

mode

is the most frequently occurring value in the data set.

median

is the number that falls exactly in the middle of a distribution of numbers.

normal curve

These statistics can be represented by a

range

is simply the largest number minus the smallest number.

Variability

refers to how much the numbers in the set differ from one another.

standard deviation

measures a function of the average dispersion of numbers around the mean and is a commonly used measure of variability.

Percentiles

express the standing of one score relative to all other scores in a set of data.

positive skew

means that most values are on the lower end, but there are some exceptionally large values.

negative skew

means the opposite: most values are on the higher end, but there are some exceptionally small values.

correlation coefficient

is a statistic that will give us such information.

Pearson correlation coefficient

is a descriptive statistic that describes the linear relationship between two attributes.

Inferential Statistics

are used to determine our level of confidence in claiming that a given set of results would be extremely unlikely to occur if the result were only up to chance.

Sample size

refers to the number of observations or individuals measured.

null hypothesis

states that a treatment had no effect in an experiment.

alternative hypothesis

is that the treatment did have an effect.

Alpha

is the accepted probability that the result of an experiment can be attributed to chance rather than the manipulation of the independent variable.

Type I error

refers to the conclusion that a difference exists when, in fact, this difference does not exist.

Type II error

refers to the conclusion that there is no difference when, in fact, there is a difference.

Stanley Milgram

conducted obedience experiments in which he convinced participants that they were administering painful electric shocks to other participants, when, in fact, no shocks were given.

Institutional Review Boards (IRBs)

assess research plans before the research is approved to ensure that it meets all ethical standards.

informed consent

they agree to participate in the study only after they have been told what their participation entails.

debriefing

in which they are told the exact purpose of their participation in the research and of any deception that may have been used in the process of experimentation.

Confidentiality

is another area of concern for psychology.