Stats Ch. 9 Vocab

t statistic

the distance of a sample mean from a population mean in terms of the estimated standard error

single-sample t test

a hypothesis test in which we compare a sample from which we collect data to a population for which we know the mean but not the standard deviation

degrees of freedom

the number of scores that are free to vary when we estimate a population parameter from a sample

replication

the repetition of a study that gives us confidence that a particular observation is true

paired-samples t test

used to compare two means when the samples are paired, or related in a clear way, including when the same participant is in both samples

order effects

refer to how a particpant's behavior changes when the dependent variable is presented for a second time

counterbalancing

minimizes order effects by varying the order of presentation of different levels of the independent variable from one participant to the next independent-samples t test is used to compare two means for a between-groups design, a situation in which each participant is assigned to only one condition

pooled variance

a weighted average of the two estimates of variance- one from each sample- that are calculated when conducting an independent-samples t test

error bars

vertical lines added to bars or dots on a graph that represent the variability of those data and give us a sense of how precise an estimate summary statistic is

analysis of variance (ANOVA)

a hypothesis test typically used with one or more nomial (and sometimes ordinal) independent variables (with at least 3 groups overall) and a scale/continuous dependent variable

F statistic

a ratio of two measures of variance: between-group variance and within-group variance

between-groups varaince

an estimate of the population variance, based on the differences among the means

within-groups variance

an estimate of the population variance, based on the differences within each of the three (or more) sample distributions

one-way ANOVA

a hypothesis test that includes both one nominal independent variable with more than two levels and a scale dependent variable

between-groups ANOVA

a hypothesis test in which there are more than two samples, and each sample is composed of different participants

within-groups ANOVA

a hypothesis test in which there are more than two samples, and each sample is composed of the same participants

Homoscedastic populations

those that have the same variance

Heteroscedastic populations

those that have different variances

source table

presents the important calculations and final results of an ANOVA in a consistent and easy-to-read format

grand mean

the mean of every score in a study, regardless of which sample the score came from

n2

an estimate of the proportion of variance in the dependent variable that is accounted for by the independent variable

omega squared (w2)

an estimate of the proportion of variance in the dependent variable that is accounted for by the independent variable; it is less biased than n2

post hoc test

a statistical procedure carried out after the null hypothesis has been rejected in an analysis of variance in which we make all possible pairwise comparisons among the means of the groups in the study

familywise Type I error rate

the probability of obtaining at least one type I error when conducting a set of comparisons

tukey HSD test

a widely used post hoc test that determines the differences between means in terms of standard error; the HSD is compared to the critical value

sphericity assumption

requires the average difference between pairs of scores to be similar across conditions