Chapter 6: Foundations: Methods and Approaches

**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.