# Psychology: from Inquiry to Understanding: Chapter 2

Prefrontal Lobotomy

Surgical procedure that severs fibers connecting the frontal lobes of the brain from the underlying thalamus.

Heuristic

Mental shortcut or rule of thumb that helps us to streamline our thinking and make sense of our world.

Naturalistic Observation

Watching behavior in real-world settings without trying to manipulate the situation.

External Validity

Extent to which we can generalize findings to real-world settings.

Internal Validity

Extent to which we can draw cause and effect inferences from a study.

Case Study

Research design that examines one person or a small number of people in depth, often over an extended time period.

Existence Proof

Demonstration that a given psychological phenomenon can occur.

Random Selection

Procedure that ensures every person in a population has an equal chance of being chosen to participate.

Reliability

Consistency of Measurement

Validity

Extent to which a measure assesses what it purports to measure.

Response Set

Tendency of research participants to distort their responses to questionnaire items.

Correlational Design

Research design that examines the extent to which two variables are associated.

Scatterplot

Grouping of points on a two-dimensional graph in which each dot represents a single person’s data.

Illusionary Correlation

Perception of a statistical association between two variables where none exists.

Experiment

Research design characterized by random assignment of participants to conditions and manipulation.

Control Group

In an experiment, the group of participants that doesn’t receive the manipulation.

Independent Variable

Variable that an experimenter manipulates.

Dependent Variable

Variable that an experimenter measures to see whether the manipulation has an effect.

Operational Definition

A working definition of what a researcher is measuring.

Placebo Effect

Improvement resulting from the mere expectation of improvement.

Blind

Unaware of whether one is in the experimental group or control group.

Experimenter Expectancy Effect

Phenomenon in which researchers’ hypotheses lead them to unintentionally bias the outcome of a study.

Double-Blind

When neither researchers nor participants are aware of who’s in the experimental or control group.

Demand Characteristics

Cues that participants pick up from a study that allow them to generate guesses regarding the researcher’s hypothesis.

Informed Consent

Informing research participants of what is involved in a study before asking them to participate.

Statistics

Application of mathematics to describing and analyzing data.

Descriptive Statistics

Numerical characterizations that describe data.

Central Tendency

Measure of the “central” scores in a data set, or where the group tends to cluster.

Mean

Average; a measure of central tendency

Median

Middle score in a data set; a measure of central tendency

Mode

Most frequent score in a data set; a measure of central tendency.

Variability

Measure of how loosely or tightly bunched scores are.

Range

Difference between the highest and lowest scores; a measure of variability.

Standard Deviation

Measure of variability that takes into account how far each data point is from the mean.

Inferential Statistics

Mathematical methods that allow us to determine whether we can generalize findings from our sample to the full population.

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