AP Psychology Uni 1

Mean

Sum of all scores divided by the number of scores. Sensitive to extreme outliers.

Median

The middle score when data is ordered from least to greatest

Mode

The most frequently occurring score(s).

Experiment

Manipulates an independent variable to measure effect on a dependent variable. Only method that proves cause-and-effect. Uses random assignment.

Case Study

In-depth study of one individual or small group. Rich detail, but cannot be generalized to the population.

Naturalistic Observation

Observing behavior in natural settings without manipulating the environment. High ecological validity; cannot control variables.

Correlation

Measures the strength and direction of a relationship between two variables. Correlation DOES NOT equal causation. Third-variable problem (confounds).

Sympathetic Nervous System

"Fight or Flight." Accelerates heart rate, dilates pupils, inhibits digestion, releases adrenaline.

Parasympathetic Nervous System

“Rest and Digest." Calms the body, slows heart rate, stimulates digestion, contracts pupils.

NREM-1

Light sleep. Theta waves. Hypnagogic sensations (falling feeling).

NREM-2

Deeper relaxation. Marked by Sleep Spindles (bursts of rapid activity) and K-complexes.

NREM-3

Deep slow-wave sleep. High-amplitude Delta waves. Sleepwalking/night terrors occur here.

REM (Paradoxical Sleep)

Rapid Eye Movement. Beta-like active brain waves. Vivid dreaming, but motor cortex is blocked (body is paralyzed).

EEG (Electroencephalogram)

Records electrical brain waves on the scalp. Great for sleep/seizure study (high temporal resolution).

PET Scan

Measures radioactive glucose consumption to reveal active brain areas. Great for functional activity.

MRI

Uses magnetic fields and radio waves to produce detailed static structural images.

fMRI

Combines MRI and PET features—tracks blood flow (oxygenation) to show structure AND functional activity in real time.

Informed Consent

Participants must know risks and agree voluntarily beforehand.

Protection from Harm

Participants must be protected from unnecessary physical/psychological distress.

Confidentiality

Individual participant data must remain anonymous/private.

Debriefing

Full explanation of the study’s purpose, hypothesis, and any deception must occur immediately after testing.

Mean 1 SD

68% of total data (34% between mean and +1 SD, 34% between mean and -1 SD).

Mean 2 SDs

95% of total data (13.5% added on each side between 1 SD and 2 SDs).

Mean 3 SDs

99.7% of total data (2.35% added on each side between 2 SDs and 3 SDs).

Qualitative

Descriptive words/text (interviews, observation logs). 

Quantitative

Numbers/statistics (test scores, times).

Independent Variable (IV)

What the researcher manipulates/changes.

Dependent Variable (DV)

What is measured (the outcome).

Correlation

Means two things vary together (predict each other).

Causation

Only controlled experiments prove causation.

Hippocampus

Processing and forming new explicit (declarative) memories.

Amygdala

Processing emotions, particularly fear and aggression.

Cerebellum

Voluntary motor movement, balance, posture, and implicit (procedural) memory.

Thalamus

Sensory relay station for all senses except smell (olfaction).

Hypothalamus

Regulates bodily homeostasis (hunger, thirst, body temperature, endocrine system/pituitary gland).

Medulla

Controls vital autonomic functions (breathing, heart rate, blood pressure).

Contralateral Hemispheric Organization

The left hemisphere processes sensory/motor functions for the right side of the body, and vice versa.

Left Hemisphere

The left hemisphere controls sensory and motor functions on the right side of the body.

Right Hemisphere

The right hemisphere controls sensory and motor functions on the left side of the body.

Random Sampling

Choosing participants from a population so everyone has an equal chance of being selected. Ensures your sample is representative and allows you to generalize results.

Random Assignment

Sorting participants into experimental or control groups by chance. Eliminates confounding variables and allows you to prove causation.

Control Group

The baseline group that does NOT receive the treatment (or receives a placebo).

Experimental Group

The group that receives the independent variable treatment.

Confounding Variable

An unintended difference between groups that affects the dependent variable (e.g., time of day, participant age).

Placebo effect

Expectation alone causes an effect.

Double-blind procedure

Neither the participant NOR the researcher knows who is in the control or experimental group (prevents experimenter bias).

Positively Skewed (Right-Skewed)

Most scores are low, but a few extremely high scores pull the tail to the right.

$$\text{Mode} < \text{Median} < \text{Mean}$$

Negatively Skewed (Left-Skewed)

Most scores are high, but a few extremely low scores pull the tail to the left.

$$\text{Mean} < \text{Median} < \text{Mode}$$

Sign (+ or -)

Indicates direction.

Positive

Variables move in the same direction (e.g., studying hours up, test scores up).

Negative

Variables move in opposite directions (e.g., exercise hours up, stress level down).

Number (0 to 1.00)

Indicates strength. -0.85 is stronger than +0.40 because absolute value determines strength, regardless of the plus or minus sign.

Illusionary Correlation

Perceiving a relationship between two variables when none actually exists (e.g., "it always rains after I wash my car").

Deception

Allowed ONLY if necessary for the study, causes no harm, and is fully revealed during debriefing.

Institutional Review Board (IRB)

The committee that must review and approve human research before it begins.

Animal Research Ethics (IACUC)

Requires clear scientific purpose, humane care/housing, and minimizing pain or distress.