psych unit zero

critical thinking

thinking that does not automatically accept arguments and

conclusions. Rather, it examines assumptions, appraises

the source, discerns hidden biases, evaluates evidence,

and assesses conclusions

hindsight bias

the tendency to believe, after learning an outcome,

that one would have foreseen it. (Also known as the

I-knew-it-all-along phenomenon.)

peer reviewers

scientific experts who evaluate a research article’s theory,

originality, and accuracy

theory

an explanation using an integrated set of principles that

organizes observations and predicts behaviors or events.

hypothesis

a testable prediction, often implied by a theory.

falsifiable

the possibility that an idea, hypothesis, or theory can be

disproven by observation or experiment.

operational definition

a carefully worded statement of the exact procedures (op-

erations) used in a research study. For example, human

intelligence may be operationally defined as what an intel-

ligence test measures. (Also known as operationalization.)

replication

repeating the essence of a research study, usually with

different participants in different situations, to see whether

the basic finding can be reproduced.

case study

a non-experimental technique in which one individual or

group is studied in depth in the hope of revealing universal

principles.

naturalistic observation

a non-experimental technique of observing and recording

behavior in naturally occurring situations without trying to

manipulate and control the situation.

survey

a non-experimental technique for obtaining the self-report-

ed attitudes or behaviors of a particular group, usually by

questioning a representative, random sample of the group.

social desirability bias

bias from people's responding in ways they presume a

researcher expects or wishes.

self-report bias

bias when people report their behavior inaccurately

sampling bias

a flawed sampling process that produces an unrepresentative sample

random sample

a sample that fairly represents a population because each

member has an equal chance of inclusion.

population

all those in a group being studied, from which random

samples may be drawn. (Note: Except for national studies,

this does not refer to a country’s whole population.)

correlation

a measure of the extent to which two factors vary together,

and thus of how well either factor predicts the other.

correlation coefficient

a statistical index of the relationship between two variables

(from 1.00 to +1.00)

variable

anything that can vary and is feasible and ethical to measure.

scatterplot

a graphed cluster of dots, each of which represents the

values of two variables. The slope 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).

illusory correlation

perceiving a relationship where none exists, or perceiving

a stronger-than-actual relationship.

regression toward the mean

the tendency for extreme or unusual scores or events to

fall back (regress) toward the average.

experiment

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 de-

pendent variable). By random assignment of participants,

the experimenter aims to control other relevant factors.

experimental group

in an experiment, the group exposed to the treatment —

that is, to one version of the independent variable.

control group

in an experiment, the group not exposed to the treatment;

contrasts with the experimental group and serves as a

comparison for evaluating the effect of the treatment.

random assignment

assigning participants to experimental and control groups

by chance, thus minimizing preexisting differences between

the different groups

single-blind procedure

an experimental procedure in which the research participants are ignorant (blind) about whether they have received the treatment or a placebo.

double-blind procedure

an experimental 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.

placebo effect

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.

independent variable

in an experiment, the factor that is manipulated; the variable

whose effect is being studied.

confounding variable

in an experiment, a factor other than the factor being

studied that might influence a study’s results.

experimenter bias

bias caused when researchers may unintentionally influence results to confirm their own beliefs.

dependent variable

in an experiment, the outcome that is measured; the

variable that may change when the independent variable is

manipulated.

validity

the extent to which a test or experiment measures or

predicts what it is supposed to.

quantitative research

a research method that relies on quantifiable, numerical

data.

qualitative research

a research method that relies on in-depth, narrative data

that are not translated into numbers.

informed consent

giving potential participants enough information about a

study to enable them to choose whether they wish to

participate.

debriefing

the postexperimental explanation of a study, including its

purpose and any deceptions, to its participants.

descriptive statistics

numerical data used to measure and describe

characteristics of groups; include measures of central

tendency and measures of variation

histogram

a bar graph depicting a frequency distribution.

mode

the most frequently occurring score(s) in a distribution.

mean

the arithmetic average of a distribution, obtained by adding

the scores and then dividing by the number of scores.

median

the middle score in a distribution; half the scores are above

it and half are below it.

percentile rank

the percentage of scores that are lower than a given score.

skewed distribution

a representation of scores that lack symmetry around their

average value.

range

the difference between the highest and lowest scores in a

distribution.

standard deviation

a computed measure of how much scores vary around the

mean score.

normal curve

a symmetrical, bell-shaped curve that describes the dis-

tribution of many types of data; most scores fall near the

mean (about 68 percent fall within one standard deviation

of it) and fewer and fewer scores lie near the extremes.

(Also called a normal distribution.)

inferential status

numerical data that allow one to generalize — to infer from

sample data the probability of something being true of a

population.

meta-analysis

a statistical procedure for analyzing the results of multiple

studies to reach an overall conclusion.

statistical significance

a statistical statement of how likely it is that a result (such

as a difference between samples) occurred by chance,

assuming there is no difference between the populations

being studied.

effect size

the strength of the relationship between two variables.

The larger the effect size, the more one variable can be

explained by the other.