PSY 511: REVIEW FROM 411 TERMS AND EQUATIONS

CONSTANT and VARIABLES

Constant

something that STAYS the SAME

Ex: number of days in Janurary

Variable

Something that CAN CHANGE

Ex: stress levels in students

Discrete Variable

only takes on whole-valued numbers

Ex: number of siblings someone has

Continuous Variable

falls in a continuum and allows fractional amounts.

Ex: Reaction time in memory test (1.23s)

SCALES OF MEASUREMENT

Nominal Scale

categories with NO ORDER just names and labels

ex: eye colour (brown, blue)

Ordinal Scale

Broken into categories on a ranked order

Movie ratings (⭐ to ⭐⭐⭐⭐⭐) — ranked order, but gaps aren’t equal.

Interval Scale

Number based, equal spacing but NO TRUE ZERO

Ex: equal spacing but 0 celcius doesn’t mean “nothing”

Ratio Scale

Number based, equal spacing but HAS A TRUE ZERO

Ex: Weight in kg — 0 kg = no weight, and 10 kg is twice as heavy as 5 kg.

Absolute Zero

means NOTHING.

Ex: 0 heartbeats = no heartbeats

2 BRANCHES OF STATS

Descriptive Stats

• summarizes/ organizes data

• homogeneity of performance= tells you how diff peoples scores are

Inferential Stats

• uses data from a sample to make conclusions about a large POPULATION

• probability based

CORRELATIONAL STUDIES

Correlational Studies

Predict the association or relationship between two variables.

Confound Variable

a 3rd variable that may indirectly impact the 2 variables in a study

EXPERIMENTAL STUDIES

Experimental Study

allows researchers to determine CAUSE AND EFFECT relationships

Dependant Variable:

what is being MEASURED

• lung health

Independant variable

What you MANIPULATE

• smoke around ppl

Control Group

did NOT receive any levels of IV

• no smoke exposure

Experimental Group

Received SOME levels of IV

• smoke exposure

Control Variables

Variables YOU KEEP THE SAME across groups to NOT mess with results

• age, diet, exercise

MEAN

Sample mean

_
𝑿 = 𝜮𝑿

———
𝒏

Population Mean

μ = 𝜮𝑿

————

𝑵

Weighted Mean

Mweighted = Σ(𝑀𝑖 ∗ 𝑛𝑖)
——————

Σ𝑛𝑖
(i = group #)

What is sensitive to extreme scores?

• Mean

• range

Estimated STANDARD DEVIATION