Stats Final Review
assumption
A belief or statement taken for granted without proof.
between-groups estimate of the population variance
S2 between. an estimate of the variance of the population of individuals based on the variation among the means of the groups studied
variance of the distribution of differences between means
S2 difference
distribution of differences between means
distribution of differences between means of pairs of samples such that, for each pair of means, one is from one population and the other is from a second population
t test for dependent means
hypothesis-testing procedure in which there are two scores for each person and the population variance is not known
A t test for dependent means would be used to compare
the level of reading comprehension of students at the beginning and at the end of a speed-reading class.
If a sample includes 27 people, the degrees of freedom used in the formula to estimate the population variance would be
26
t distribution
A distribution specified by degrees of freedom used to model test statistics for the sample mean, differences between sample means, etc.
two-tailed test
A hypothesis test in which rejection of the null hypothesis occurs for values of the test statistic in either tail of its sampling distribution.
one-tailed test
A hypothesis test in which rejection of the null hypothesis occurs for values of the test statistic in one tail of its sampling distribution.
One-directional hypothesis
A hypothesis that indicates that an independent variable will either have more of an effect on a dependent variable, or less. It can't be both.
repeated measures design
An experiment using a within-groups design in which participants respond to a dependent variable more than once, after exposure to each level of the independent variable.
weighted average
Average of data that adds factors to reflect the importance of different values.
main effect
In a factorial design, the overall effect of one independent variable on the dependent variable, averaging over the levels of the other independent variable.
The comparison distribution in a test for a single sample (N>1) is a distribution of ______
Means
The comparison distribution in a T test for dependent means (N>1) is a distribution of
Means of difference scores
nondirectional hypothesis
Predicts the existence of a relationship, not its direction
standard deviation of the distribution of differences between means
S difference
Which of the following statements is true about T distributions?
The larger the sample size, the more a t distribution resembles a normal curve.
within-groups degrees of freedom (denominator)
The number of degrees of freedom associated with the within-groups estimate of variance; equivalent to the number of cases minus the number of groups. df within.
degrees of freedom
The number of individual scores that can vary without changing the sample mean. Statistically written as 'N-1' where N represents the number of subjects.
In which of the following situations would a T test for independent means be conducted?
a comparison of scores of participants in a memory study where one group is assigned to learn the words in alphabetical order and another group is assigned to learn the words in order of length of the word
interaction effect
a result from a factorial design, in which the difference in the levels of one independent variable changes, depending on the level of the other independent variable; a difference in differences
t test
a statistical test used to evaluate the size and significance of the difference between two means
grouping variable
a variable that separates groups in analysis of variance
post-hoc tests
additional significance tests conducted to determine which means are significantly different for a main effect
factorial analysis of variance
analysis of variance for a factorial research design
two-way analysis of variance
analysis of variance for a two-way factorial research design
analysis of variance (ANOVA)
analysis of variance test used for designs with three or more sample means
between-groups degrees of freedom (numerator)
df between. The number of degrees of freedom associated with the estimate of between-groups variance; equivalent to the number of groups minus 1.
biased estimate
estimate of a population parameter that is likely systematically to overestimate or underestimate the true value of the population parameter
unbiased estimate of the population variance (S^2)
estimate of the population variance, based on sample scores, which has been corrected so that it is equally likely to overestimate or underestimate the true population variance
within-groups estimate of the population variance (S2 within)
estimate of the variance of the population of individuals based on the variation among the scores in each of the actual groups studied
two-way factorial research design
factorial research design in analysis of variance with two variables that each divide the groups
t test for a single sample
hypothesis-testing procedure in which a sample mean is being compared to a known population mean and the population variance is unknown
t test for independent means
hypothesis-testing procedure in which there are two separate groups of people tested and in which the population variance is not known
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
When estimating the variance of a population from the sample, the sample variance cannot be used directly because
it tends to be slightly too small—it underestimates the population variance.
grand mean (GM)
mean of the group means
F distribution
positively skewed distribution derived from a sampling distribution of F ratios
difference scores
scores representing the difference between subjects' performance in one condition and their performance in a second condition
planned contrasts
statistical tests that allow us to test comparisons between groups that we predicted ahead of time. These tests have the added benefit of allowing you to combine two conditions so that you can compare it to a third
robust
strong
the main difference between a Z score and a T score is that
t scores are used when the population variance is unknown
F table
table of cutoff scores on the F distribution
t table
table of cutoff scores on the t distribution for various degrees of freedom, significance levels, and one- and two-tailed tests
marginal mean
the average of all participants on one level of the independent variable, ignoring the other independent variable
cell mean
the average score of the participants in a single cell
A t test for a single sample would be used to compare
the hours that "C" average students spend on Facebook each week compared with students in general.
When conducting a T test for independent means, a typical research hypothesis might be
the mean of Population 1 is greater than the mean of Population 2.
F ratio
the ratio of between-groups variance to within-groups variance
factorial research design
way of organizing a study in which the effects of two or more variables are studied at once by making groupings of every combination of the variables