# test 3

## 19 terms

### t test

testing procedure where the population variance is unknown.

### single sample

testing procedure where a sample mean is being compared to a known population mean and population variance is unknown

### biased estimate

estimate of population parameter that is likely to overestimate or underestimate the true value of the population parameter.

### unbiased estimate of the population variance

estimate of the population variance, based on sample scores, which have been corrected so that it is equally likely to over or under estimate the true population variance.

### degrees of freedom

number of scores free to vary when estimating a population parameter

### t table

table of cutoff scores on the t distribution for various degrees of freedom, significance levels, and one and two-tailed tests.

### t distribution

curve that is the comparison distribution used in a t test

### t score

on a t distribution, number of standard deviations from the mean

### repeated - measures design

each person is tested more than once

### dependent means

testing procedure which their is two scores for each person and the population variance is not known

### difference scores

difference between a person's score on one testing and the same person's score on another testing

### robustness

extent to which a particular hypothesis - testing procedure is reasonably accurate

### independent mean

testing procedure where there are two separate groups of people tested and in which the population variance is not known.

### distribution of differences between means

distribution of differences between means of pairs of means.

### pooled estimate of the population variance

in a t test for independent means, weighted average of the estimates of the population variance from two samples.

### weighted average

average in which the scores being averaged do not have equal influence on the total.

### variance of the distribution

one of the numbers figured as part of a t test for independent means

### standard deviation of the distribution

in a t test for independent means, square root of the variance of the distribution of differences between means.

### harmonic mean

special average influenced disproportionately by smaller numbers.