Unit Zero - Research Methods in Psychology

Independent Variable

what you change in an experiment (ex: changing how much sleep students get to see how it affects test scores)

Dependent Variable

what you measure (the results) (ex: measuring students' test scores)

Random Assignment

randomly putting people into groups (ex: flipping a coin to decide who gets the new medicine)

Random Sample

Randomly picking people to study (ex: picking 100 students from a school at random for a survey)

Confounding Variable

Extra things that could mess up results (ex: students drinking coffee before a sleep experiment)

Correlation & Causation

2 things are related but one doesn't cause the other (ex: Ice cream sales & drowning deaths both rise in summer, but ice cream doesn't cause drowning)

Statistical Significance

results is likely real, not due to change (ex: a drug study shows big improvement with p-value < 0.05)

Placebo Effect

feeling better bc/ you think you got treatment (ex: taking a sugar pill but feeling less pain)

Control Group

the group in an experiment that does not receive the test variable

Positive Correlation

a relationship where if one variable increases, the other does too

Negative Correlation

a relationship where if one variable increases, the other decreases

Mean

average ((2+4+6)/3 = 4)

Median

middle number (In 1, 3, 5 — median is 3)

Mode

Most common number (In 2, 2, 3, 4 — mode is 2)

Standard Deviation

how spread out numbers are (small deviation = scores are close together)

Positive Skew

Tail points right (high side) (Most people score low, a few score super high)

Negative Skew

Tail points left (low side) (Most people score high, a few score really low)

Normal Distribution

Bell-shaped curve (Most students get a C on a hard test; few get As or Fs)

Correlation Coefficient (r value)

number showing strength of relationship (r = 0.8 means a strong positive relationship)

Biological Perspective

Behavior is from body and brain (ex: depression caused by low serotonin)

Behavioral Perspective

Behavior is learned (ex: a child is polite because parents reward good manners)

Cognitive Perspective

Behavior is from thinking (ex: believing you're bad at math makes you avoid math)

Humanistic Perspective

People want to grow and succeed ( ex: therapy helps people discover their best self)

Psychodynamic Perspective

Behavior is from unconscious and childhood (ex: fear of dogs because of a forgotten childhood bite)

Sociocultural Perspective

Behavior is from society and culture (ex: being more emotional in a culture that values expressing feelings)

Evolutionary Perspective

Behavior helped ancestors survive (ex: fear of snakes because it helped early humans stay alive)

Biopsychosocial Perspective

Behavior = biological + mental + social (ex: depression explained by brain chemistry, bad thoughts, and stressful life events)

Hindsight Bias

"I knew it all along" feeling (ex: saying "I knew they would break up!" after they do)

Confirmation Bias

Only noticing info that supports you (ex: only reading news that matches your opinions)

Social Desirability Bias

Giving "good" answers to look better (ex: lying on a survey saying you recycle more than you do)

Third Variable Problem

A third thing actually causes it (ex: ice cream sales and sunburns are both caused by hot weather)

Ethics

-informed consent

-confidentiality

-deception

-debriefing

-IRB approval

Empirical Evidence

Based on experiments and data (ex: proving a new therapy works through real experiments)

Validity

Measuring what you say you're measuring (ex: a math test actually measuring math skills, not reading ability)

Scatterplot

A graph showing relationships (ex: scatterplot of studying hours vs. GPA)

Regression to the Mean

Extreme values tend to move closer to the average later (ex: a student scores super high on one test but gets a more average score on the next one)

Percentile Rank

The percentage of scores lower than a specific score (ex: if you're in the 90th percentile on a test, you scored better than 90% of people)

Bimodal Distribution

A data set with two clear peaks or modes (ex: a survey about favorite ice cream flavors shows two big groups: one loves chocolate, one loves vanilla)

Effect Size

How strong the relationship is between two variables (ex: a study finds a big effect size between studying more hours and getting better grades — studying really helps!)