Unit 2 Research Methods

standard deviation (p.58)

a computed measure of how much scores vary around the mean score.

confounding variable (p.52)

a factor other than the independent variable that might produce an effect in an experiment.

sampling bias (p.43)

a flawed sampling process that produces an unrepresentative sample.

scatterplot (p.46)

a graphed cluster of dots, each of which represents the values of two variables. The slop of the points suggests the direction of the relationship between the two variables. The amount of scatter suggests the strength of the correlation (little scatter indicates high correlation).

correlation (p.46)

a measure of the extent to which two factors vary together, and thus of how well either factor predicts the other.

experiment (p.51)

a research method in which an investigator manipulates one or more factors (independent variables) to observe the effect on some behavior or mental process (the dependent variable). By random assignment of participants, the experimenter aims to control other relevant factors.

random sample (p.43)

a sample that fairly represents a population because each member has an equal chance of inclusion.

operational definition (p.39)

a statement of the procedures (operations) used to define research variables. For example, human intelligence may be operationally defined as what an intelligence test measures.

correlation coefficient (p.46)

a statistical index of the relationship between to things (from -1 to +1).

statistical significance (p.60)

a statistical statement of how likely it is that an obtained result occurred by chance.

normal curve (p.59)

a symmetrical, bell-shaped curve that describes the distribution of many types of data; most scores fall near the mean (68% fall within one standard deviation of it) and fewer and fewer near the extremes.

survey (p. 42)

a technique for ascertaining the self-reported attitudes or behaviors of a particular group, usually by questioning a representative, random sample of the group.

hypothesis (p.38)

a testable prediction, often implied by a theory.

population (p.43)

all the cases in a group being studied, from which samples may be drawn. (Note: Except for national studies, this does not refer to a country's whole population.)

informed consent (p.68)

an ethical principle that research participants be told enough to enable them to choose whether they wish to participate.

double-blind procedure (p.51)

an experiment procedure in which both the research participants and the research staff are ignorant (blind) about whether the research participants have received the treatment or a placebo. Commonly used in drug-evaluation studies.

theory (p.38)

an explanation using an integrated set of principles that organizes observations and predicts behaviors or events.

case study (p. 40)

an observation technique in which one person is studied in depth in the hope of revealing universal principles.

random assignement (p.51)

assigning participants to experimental and control groups by chance, thus minimizing preexisting differences between those assigned to the different groups.

placebo effect (p.52)

experimental results caused by expectations alone; any effect on behavior caused by the administration of an inert substance or condition, which the recipient assumes is an active agent.

experimental group (p.51)

in an experiment, the group that is exposed to the treatment, that is, to one version of the independent variable.

control group (p.51)

in an experiment, the group that is not exposed to the treatment; contrasts with the experimental group and serves as a comparison for evaluating the effect of the treatment.

inferential statistics (p.60)

numerical data that allow one to generalize— to infer from sample data the probability of something being true of a population.

descriptive statistics (p.57)

numerical data used to measure and describe characteristics of groups. Includes measures of central tendency and measures of variation.

naturalistic observation (p. 40)

observing and recording behavior in naturally occurring situations without trying to manipulate and control the situation.

replication (p. 39)

repeating the essence of a research study, usually with different participants in different situations, to see whether the basic finding extends to other participants and circumstances.

range (p.58)

the difference between the highest and lower scores in a distribution.

independent variable (p.52)

the experimental factor that is manipulated; the variable whose effect is being studied.

validity (p.53)

the extent to which a test measures or predicts what it is supposed to.

dependent variable (p.52)

the outcome factor; the variable that may change in response to manipulations of the independent variable.

illusory correlation (p.50)

the perception of a relationship where none exists.

debriefing (p.68)

the postexperimental explanation for a study, including its purpose and any deceptions, to its participants.

hindsight bias (p. 31)

the tendency to believe, after learning an outcome, that one would have foreseen it. (Also known as the I-knew-it-all-along phenomenon.)

critical thinking (p.35)

thinking that does not blindly accept arguments and conclusions. Rather, it examines assumptions, discerns hidden values, evaluates evidence, and assesses conclusions.