Unit 4 Research Methods

Scientific method

A systematic process of asking questions, forming hypotheses, collecting data, and drawing conclusions.

Hypothesis

A specific, testable prediction about the relationship between variables.

Theory

An explanation that organizes observations and predicts future events.

Operational definition

A precise description of how a variable will be measured or manipulated.

Replication

Repeating a study to determine whether similar results can be obtained.

Variable

Any factor that can change or vary in a study.

Descriptive research

Research that observes and records behavior without manipulating variables.

Experimental research

Research that manipulates an independent variable to investigate cause and effect.

Correlational research

Research that examines relationships between variables without manipulating them.

Case study

An in-depth investigation of one person, group, or event.

Naturalistic observation

Observing behavior in a natural setting without interfering.

Laboratory observation

Observing behavior in a controlled environment.

Survey

A research method that gathers self-reported information through questions.

Archival research

Research using existing records, documents, or previously collected information.

Independent variable

The variable manipulated by the researcher.

Dependent variable

The variable measured to determine the effect of the independent variable.

Confounding variable

An outside factor that may influence the dependent variable and interfere with conclusions.

Experimental group

The group that receives the treatment or manipulation.

Control group

The comparison group that does not receive the experimental treatment.

Placebo

An inactive treatment that resembles the real treatment.

Placebo effect

A change caused by expectations rather than an active treatment.

Single-blind study

A study in which participants do not know their treatment assignment.

Double-blind study

A study in which neither participants nor the researchers interacting with them know treatment assignments.

Experimenter bias

When researcher expectations influence a study or its results.

Participant expectations

When participants' beliefs about a study influence their behavior.

Positive correlation

A relationship in which two variables tend to increase or decrease together.

Negative correlation

A relationship in which one variable tends to increase as the other decreases.

Correlation coefficient

A number from -1 to +1 indicating the direction and strength of a linear relationship.

Strong correlation

A correlation coefficient close to -1 or +1.

Weak correlation

A correlation coefficient close to zero.

Correlation versus causation

A relationship between variables does not prove that one causes the other.

Informed consent

Participants receive relevant study information and voluntarily agree to participate.

Debriefing

Explaining the study to participants afterward, including any deception used.

Deception

Misleading or withholding some study information when ethically justified and followed by appropriate debriefing.

APA

American Psychological Association, which establishes professional ethical guidelines.

Research ethics

Standards protecting participants' rights, welfare, and safety.

Mean

The arithmetic average, calculated by adding values and dividing by the number of values.

Median

The middle value when data are arranged in order.

Mode

The most frequently occurring value in a data set.

Range

The largest value minus the smallest value.

Measures of central tendency

Mean, median, and mode; statistics describing a typical or central value.

Standard deviation

A measure of how spread out data values are around the mean.

Sigma (σ)

The symbol commonly used for population standard deviation.

Low standard deviation

Scores tend to be clustered close to the mean.

High standard deviation

Scores tend to be more spread out from the mean.

Histogram

A graph using adjacent bars to display frequencies of numerical values or intervals.

Normal distribution

A symmetrical, bell-shaped distribution with most scores near the mean.

Positively skewed distribution

A distribution with a longer tail extending to the right.

Negatively skewed distribution

A distribution with a longer tail extending to the left.

Bimodal distribution

A distribution with two distinct peaks.

Empirical rule

Approximately 68%, 95%, and 99.7% of normally distributed values fall within one, two, and three standard deviations of the mean.

Z-score

The number of standard deviations a score is above or below the mean.

Z-score formula

Z = (individual score - mean) / standard deviation.

Positive z-score

A score above the mean.

Negative z-score

A score below the mean.

Population

The entire group a researcher wants to understand.

Sample

A subset of a population selected for study.

Representative sample

A sample that reflects relevant characteristics of the larger population.

Generalizability

The extent to which findings apply beyond the studied sample.

Sample size

The number of observations or participants in a study.

Descriptive statistics

Numerical methods used to organize and summarize collected data.

Inferential statistics

Methods used to draw conclusions about a population from sample data.

Statistical significance

Evidence that an observed result would be unlikely under a specified null hypothesis.

Reliability

The consistency of a measurement across repeated uses.

Validity

The extent to which a measurement assesses what it is intended to measure.

Content validity

The extent to which a test adequately represents the content it should assess.

Predictive validity

The extent to which a measure predicts a relevant future outcome.

Research scenario: Music and test scores

If music is manipulated and test scores are measured, music is the independent variable and test scores are the dependent variable.

Research scenario: Exercise and stress

If researchers manipulate exercise and measure stress, exercise is the independent variable and stress is the dependent variable.

Research scenario: Camera light affects rats

An unexpected camera light influencing rat activity is a possible confounding variable.

Research scenario: Old newspapers

Analyzing historical newspapers to study behavior is archival research.

Research scenario: Detailed investigation of one student

Using interviews, observations, and records to investigate one student is a case study.

Research scenario: Participants and researchers unaware of treatment assignments

This describes a double-blind study.

Calculation: Mean of 2, 6, 6, 8, 9, 11

7.

Calculation: Mode of 2, 6, 6, 8, 9, 11

6.

Calculation: Mean 60, SD 10, score 70

Z-score = +1.

Calculation: Mean 85, SD 6, z-score -0.5

Raw score = 82.