AP Psychology Unit 2 Scientific Methodology

Histogram

a bar graph depicting a frequency distribution.

Operational Definition

a carefully worded statement of the exact procedures used in a research study. For example, human intelligence may be operationally defined as what an intelligence test measures.

Standard Deviation

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

Case Study

a descriptive technique in which one individual or group is studied in depth in the hope of revealing universal principles.

Confounding Variable

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

Sampling Bias

a flawed sampling process that produces an unrepresentative sample.

Scatterplot

a graphed cluster of dots, each of which represent the values of two variables. The slope of the point suggests the direction of the relationship between the two variables. The amount of scatter suggests the strength of the correlation.

Correlation

a measure of the extent to which two variables change together, and thus of how well either variable predicts the other.

Skewed Distribution

a representation of scores that lack symmetry around their average value.

Experiment

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

Random Sample

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

Correlation coefficient

a statistical index of the relationship between two variables

Statistical Significance

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

Normal Curve (Normal Distribution)

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

Survey

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

a testable prediction, often implied by a theory (educated guess)

Population

all those in a group being studied, from which samples may be drawn (doesn't not refer to a country's whole population)

Informed Consent

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

Double-blind procedure

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

Theory

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

Random Assignment

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

Placebo Effect

experimental result caused by expectation 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

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.

Inferential Statistics

numerical data that allows one to generalise, to infer from sample data the probability of something being true of a population.

Descriptive Statistics

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

Naturalistic Observation

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

Replication

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

Mean

the arithmetic average of a distribution, obtained by adding the scores and then dividing by the number of scores.

Range

the difference between the highest and the lowest scores in the distribution

Culture

the enduring behaviors, ideas, attitudes, values and traditions shared by a group of people and transmitted from one generation to the next.

Debriefing

the experimental explanation of a study, including its purpose and any deceptions, to its participants.

Independent Variable

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

Validity

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

Median

the middle score in a distribution; half the scores are above it and half are below it.

Mode

the most frequently occurring scores in a distribution.

Dependent Variable

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

Illusory Correlation

the perception of a relationship where none exists

Hindsight Bias

the tendency to believe, after learning an outcome, that one would have foreseen it. ("I knew it all along")

Critical Thinking

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