PSY 115 Stats Formula Notes

Experimental Design

Research creates group, giving each a different task, to see who does best at the task - cause & effect

Longitudial Study

Where researchers study longer over time like 6 weeks or 20 years

Rounding rules

4 decimal places beyond original numbers

Sample

Group from population

Population

Parameter, everyone in the group of people the researcher is interested in studyingS

Sampling methods

Random

Stratified

Random sampling

Every subject has the same chance of being picked

Stratified sampling

Places population into groups and then samples - more representitive

Convenience Sampling

What samples are available - always a bias

Variable

Anything you can study in research

Qualitative Variable

Catagorial - dunkin vs starbucks

Quantitative Variable

Represented by a number - age

Discrete Variable

All qualitative, some quantitative - if a number its whole

Continuous Variable

Only a quantitative - if a number, could go on forever

Levels of measurement

Nominal

Ordinal

Interval

Ratio

Nominal

Catagorical data - race, gender, favorite class - each variable defined by a number instead of a name

Ordinal

Number means something - rank ordering, position in a race - not an equal distance between numbers

Interval

Continuous scale - equal distance between two scores - 1 inch to 2 inches, 2 inches to 3 inches - numbers have no true zero, could have no zero or negative numbers

Ratio

Continuous scale - equal distance between two scores - 1 inch to 2 inches, 2 inches to 3 inches - numbers based, has a true zero and no negative numbers - 0 = nothing

Quasi - Experimental

At least one independent variable is not randomly assigned

N

Total number of scores

∑

Summation - add up all the scores - ∑F = N

Relative frequency

Proportion - F/N

Cumulative frequency

How many were at a specific score and below - very top number will always be the same as N

Percentile

Percent version of CF - CF/N*100 - round to 2 decimal places

In question, if asked how many _______

Look to Frequency

In question, if asked proportion

Look to Relative Frequency

In question, if asked what percent

Look to percentile