PSY 223 - key topics / ideas

Descriptive Statistics

Summarization of observations

Internal Statistics

Using descriptive stats to make predictions about unknown data

Population

set of all individuals, items, data, of interest

Sample

Set of collected indviduals, items, or data taken from a population of interests

Sample error

The discrepancy, or amount of error, that exists in a sample statistic & the corresponding population parameter

We must look for what during a difference

True difference vs chance difference

Population parameter

A characteristic (typically a numerical one) that describes a population

Sample statistic

a characteristic (numeric usually) that describes a sample

Scales of measurement

Rules that describes the property of numbers

Scale of measurement is characterized by 3 properties

order, differences, and ratio

Order

does a larger number indicate a greater value than a smaller number?

Differences

Does subtracting two numbers represent some meaningful value

ratio

does dividing (taking the ratio of) two numbers represent some meaningful value

Nominal

values assigned to categories

categories that cant be ranked

The # assigned have no intrinsic meaning

ordinal

assigns #’s to categories that correspond to ranks

responses cannot be ranked from high to low (vice versa)

the distance between the first & secondary category is not necessary the same as the distance between the second and third categories & so on

Interval

have the properties of oridinal scales

however the distance between the first and secondary is the category is the same as the 2nd and 3rd category and so on

Ratios

Have properties of interval scales

or have items classified into ‘zero” category

EX: weight, height, no weight or height, if its zero !

continuous data

measured along a continium any place beyond the decimal point

Desecrete

measured in whole points or categories that are not disturbed along a continuum

quantitative

varies by amounts measured numerically and is often collected by measuring or counting

qualtative

varies by class; often represented as a label to describe non numerical aspects of a phenomena