Psych Testing ch.2

Statistics

A numerical representation of info

Statistical methods

Quantifying and applying numbers to data in order to organize, summarize, and analyze information

What are the two types of statistics?

Descriptive and Inferentical

Variable

Anything that can take on more than one value

What are the various types of variables?

Quantitative

Qualitative

Continuous

Discrete

Observable

Latent

Population

Large group of people

Sample

Randomly selected group from the population

What are the scales of measurement?

Magnitude

Equal intervals

Absolute 0

What are the different types of scales?

Ordinal

Nominal

Interval

Ratio

Descriptive stats

Help us with describing what has occurred

Inferential stats

Allow us to speculate about what cannot be directly observed or measured.

Magnitude

It is a measure of “moreness” of a given quantity

Equal intervals

The difference between two points at any place on the scale has the same meaning as the difference between two other points that differ by the same number of scale units.

Absolute 0

It is an absence of the property being measured rather than an arbitrary, relative zero

Nominal

No scale quantities

Examples: names, lists of words

Ordinal

Scale qualities: magnitude

Examples: rank ordered, likert scales

Interval

Scare qualities: magnitude, equal intervals

Examples: temperature

Ratio

Scale qualities: magnitude, equal intervals, absolute 0

Example: age, height, weight

Distribution

A set of scores

Frequency distribution

A distribution ranked by the number of responses or each variable

Group frequency distribution

A distribution that groups ranges of scores. Often used when there is a high number of discrete scores.

Symmetrical

One side of the curve mirrors the other

Asymmetrical

Skew exists in the curve

Kurtosis

A statistic that reflects the peakeness or flatness of a distribution relative to a normal distribution

Standard score

Refers to scores that have been converted is an interpretable scale that has a set mean and standard deviation

Linear transformation

Uses a direct relationship between scores

Area transformations

Uses the area to create scale scores

Raw score

Number of correct answers or behaviors observed

Percentiles

Scores that reflect the rank or position of an individual’s test performance on a continuum from 0 to 99 in comparison to others who took the test

Percentages

A form of raw score that reflects the numbers of correct responses obtained out of the total possible number of correct responses on a test

What are measures of central tendency?

Mean, median and mode

Variability

The degree to which scores differ from one another

Measures of variability

The degree to which scores differ from the mean. There are several methods for measuring variability

What is the mean and standard duration of a t-score?

Mean: 50

S.D: 10