1. Chapter 1 - Psychological Statistics

Nominal

Nominal

Number is assigned to represent something or someone

Ordinal

Convey order or rank alone

Interval

No true zero and distributed in equal units

Ratio

Have a true zero and are distributed in equal units

Population

Entire set of individuals or items of interest

Sample

Representative subset of a population

Data from a population are termed

parameters

Data from a sample are termed

statistics

A researcher tests whether the dosage level of a some drug (low, high) <i>causes</i> significant differences in health.

Experiment

A researcher tests whether citizens of differing political affiliations (Republican, Democrat) will show differences in attitude toward morality.

Quasi-experiment

A researcher measures the relationship between annual income and life satisfaction.

Correlational

A researcher assesses how students perform on exams in relation to how much time they spend watching lecture videos.

Correlational

Experimental Method

-Experiment- any study that demonstrates cause

-Cause has 3 components:
1. manipulation
2. randomization
3. comparison/control

-Random Assignment renders groups equivalent (Requirement 2)

-At least 2 groups (Requirement 3)
-Experimental Group
-Control Group

Independent Variable (IV)

Is changed/controlled

Dependent Variable (DV)

-Doesn't change
-Is tested and measured
-Proposed effect

-Operational Definition-how will DV be measured

-Reading achievement Scores

Experimental Group

-Exposed to IV
-New Teaching Method

Control Group

-Not exposed to IV
-Traditional Teaching Method

Quasi-Experiments

-A non-manipulated IV (classification variable)
-Lack of random assignment to groups; and/or
-Lack of control (comparison) group

~Example: Do boys and girls (IV) differ in number of aggressive behaviors (DV)?

~Example: Are there differences between 20-year-old and 40-year-olds (IV) in reaction time (DV)?

Correlational

1. Quantifies the strength and direction of a relationship between two (or more) variables (x and y)
2. Variables measured as they naturally occur
3. Lack of random assignment

-Lacks control to determine cause-effect

-CORRELATION DOES NOT IMPLY CAUSATION!!!

Statistics

Mathematical procedures used to summarize, analyze and interpret observations

Data

Numbers to observations according to rules called "scores" or "raw scores"

Classification of Quantitative Data

Quantitative Data
↓------------------------------↓
Categorical Quantifiable
↓------------↓ ↓-------------↓
Nominal Ordinal Discrete Continuous
↓------------------↓
Interval Ratio

Descriptive

-Summarize and organize scores
-Presented graphically, tables, single values

Inferential

-Allows sample results to be generalized to representative populations
-Infer meaning

Descriptive Statistics

Summarize sample results

Inferential Statistics

Generalize to populations

Sample and Population Example

(SAMPLE) 200 undergraduate psych. students→ (POPULATION) undergraduate psych. students

(SAMPLE)150 patients with depression → (POPULATION) depression patients

Science

-Systematic study of relationships
-Applied using the research method