Inferential Statistics (Ch. 12)
Used to infer the characteristics of the population

Some terminology:
Parameters - a characteristic of the population
Statistic - a characteristic of your sample

Parametric statistics estimate values of the population from characteristics of a sample

These estimates are based on the following assumptions:
1. the population values are normally distributed
2. interval or ratio measurements are made

Nonparametric statistics make no assumptions about the distribution of scores in your sample and can be used with ordinal or nominal data

Inferential Statistics are used to estimate the probability that observed samples come from the same population. You calculate the observed value of the statistic (based on sample data) and compare this to critical values (or with computer programs, you are simply given the probability that the calculated statistic (or an even unlikely one) occurred by chance.

Parametric Inferential statistics make assumptions that:
1. scores have been sampled randomly
2. the sampling distributions are normal
3. the within-groups variances are homogeneous
violations of these assumptions will bias the test