Psychology Research Methods and Statistical Analysis: Key Concepts and Techniques

Critical thinking

The Scientific attitude - curiosity + skepticism + humility prepares us to think harder and smarter.

Hindsight bias

(also known as the l-knew-it-all-along phenomenon) is the tendency to believe, after learning an outcome, that we would have foreseen it.

Peer reviewers

other scientists who are experts - evaluate a study'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 (operations) used in a research study. For example, human intelligence may be operationally defined as what an intelligence test measures.

Replication

repeating the essence of the 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-reported 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.

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 graphical cluster of dots, each of which represents the value of the 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 suggests a 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 processes (The dependent variable). By random assignment of participants, the experimenter aims to control the 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 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 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 the 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

is 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.

Experimental 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 is supposed to happen.

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 post-experimental 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; including measures of central tendency and measures of variation.

Histogram

a bar graph depicting a frequency distribution

Mode

the most frequently occurring scores (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 the lowest scores in a distribution.

Standard deviation

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

Normal curve

A symmetrical, bell-shaped curve describes the distribution 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.

Inferential statistics

numerical data that allow one to generalize and 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.