PSYCH 2500 Key Concepts

Constructs

An abstract attribute, theory, or hypothetical mechanism

Operational definitions

The exact steps, tools, or behaviors used to measure the construct indirectly (Ex: IQ Score, Mental Health Test Score, Hours of Sleep)

Descriptive statistical analysis

Summarizes and describes core features of a dataset (Mean, median, mode, range, variance, standard deviation, frequency, skewness)

Inferential statistical analysis

Uses data from a small group (a sample) to make smart guesses and test ideas about a much larger group (a population)

Ex: Hypothesis testing, confidence intervals, regression, correlations

Population

The entire group you want to study

Sample

A sample is a smaller subset chosen from that group to collect data

Parameter

Describes an entire population

Statistic

Describes a small sample of the population

Systematic differences

A predictable, non-random deviation or gap between sets of data, groups, or measurements

(Random) Sampling error

The difference between a sample statistic (like a sample average) and the actual population parameter (like the true population average) that happens just because you studied a small group instead of the whole population

Correlational method

A statistical way to measure the strength and direction of a relationship between two or more variables

Experimental method

A structured research procedure used to test cause-and-effect relationships by manipulating one variable and measuring changes in anothe

Non-experimental method

A type of research where the researcher measures variables as they naturally occur without manipulating any independent variables or randomly assigning participants to conditions

Independent variable

The variable being manipulated

Dependent variable

The factor that a researcher measures or tests in an experiment to see how it responds to changes made to the independent variable

Quasi-independent variable

A pre-existing trait or natural condition that a researcher studies like an independent variable, but cannot actively change or randomly assign

Extraneous variable

any factor in a research study that is not the main focus of the investigation but could still affect the dependent variable

Counterbalancing

An experimental technique used in within-subjects (repeated-measures) designs to control for order and sequence effects

Bootstrapping

Figuring out what to expect based on chance alone

Null

The hypothesis that nothing special has occurred

Alpha criterion

The probability of a result being more extreme than the cutoff

Discrete variable

Separate, indivisible categories, no values can exist between neighboring values

Continuous variable

Infinite # of possible values that fall between any 2 observed values

Real limits

Define the precise boundaries of a single score when data is measured on a continuous scale

The boundary between 2 whole # sits exactly at the .5 mark

Each score has an upper limit and a lower limit

Nominal scale

Having to do with names, no quantitative differences

Ex: College majors

Ordinal scale

Set of categories that are organized in an ordered sequence

Ex: Small, medium, large

Interval scale

Ordered categories of the same size, zero is arbitrary, does not indicate a zero amount, 0 degrees does not mean temperature

Ratio scale

Interval with an absolute zero point