Statistics

Question 1

Mann-Whitney U Test

Answer 1

one independent variable - two independent groups

one dependent variable - rank-ordered data

Question 2

Wilcoxon Matched-Pairs Signed-Ranks Test

Answer 2

one independent variable - two correlated groups

one dependent variable - rank-ordered data

Question 3

Kurskal-Wallis Test

Answer 3

one independent variable - two or more independent groups

one dependent variable - rank-ordered data

Question 4

Mann-Whitney is the nonparametric version of ______

Answer 4

the t-test for independent samples

Question 5

Wilcoxon is the nonparametric version of ________

Answer 5

the t-test for correlated samples

Question 6

Kurskal-Wallis is the nonparametric version of ________

Answer 6

the one-way ANOVA

Question 7

Parametric tests are measured on _____ & _____ scales.

Answer 7

interval & ratio

Question 8

Nonparametric tests are measured on _______ & _______ scales.

Answer 8

nominal & ordinal

Question 9

Type I error

Answer 9

investigator rejects a true null hypothesis

Question 10

Type II error

Answer 10

investigator fails to reject a false null hypothesis

Question 11

3 predictions of the Central Limit Theorem

Answer 11

regardless of the shape of the distribution of individual scores in the population, as the sample size increases, the sampling distribution of the mean approaches a normal distribution

mean of the sampling distribution of the mean is equal to the population mean

standard deviation of the sampling distribution of the mean is equal to the population standard deviation divided by the square root of the sample size

Question 12

formula for standard error of the mean

Answer 12

SEM = standard deviation / square root of N

Question 13

variance

Answer 13

standard deviation squared

Question 14

percentage of scores within one standard deviation

Answer 14

68

Question 15

percentage of scores within two standard deviations

Answer 15

95

Question 16

percentage of scores within three standard deviations

Answer 16

99

Question 17

t-test

Answer 17

used to compare only two means at a time

a study including more than two means (more than two levels of the IV) would require multiple t-tests and would increase experimentwise error rate

Question 18

ANOVA

Answer 18

used to compare two or more means

simultaneously makes all comparisons while holding the probability of making a Type I error at the level of significance set by the experimenter

Question 19

one-way ANOVA

Answer 19

used when a study includes one independent variable

Question 20

factorial ANOVA

Answer 20

used when a study includes two or more independent variables

Question 21

Cohen’s d

Answer 21

measure of the difference between tow groups in terms of standard deviation units

small effect size = 0.2
medium effect size = 0.5
large effect size = 0.8

Question 22

Eta squared

Answer 22

indicates the percent of variance in the outcome variable that is accounted for by variance in the treatment

Question 23

Pearson r

Answer 23

data on both variables represents a continuous scale (interval or ratio data)

Question 24

Spearman rho

Answer 24

both variables are ranks

Question 25

Point biserial

Answer 25

one variable is a true dichotomy and the other is continuous

Question 26

Biserial

Answer 26

one variable is an artificial dichotomy and the other is continuous

Question 27

eta

Answer 27

the variables are both continuous and have a nonlinear relationship

Question 28

external validity

Answer 28

the degree to which a study’s results can be generalized to other people, settings, conditions, etc.

Question 29

internal validity

Answer 29

the degree to which a study allows an investigator to conclude that observed variability in a dependent variable is due to the independent variable rather than to other factors

Question 30

moderator variables

Answer 30

affect the strength or direction of the relationship between independent and dependent variables

if a treatment works better for men than for women, gender is a moderator variable

Question 31

mediator variables

Answer 31

explain the relationship between independent and dependent variables

a parenting style might lead to better school performance because it leads to more self efficacy beliefs. so self-efficacy beliefs are the mediator in the relationship between parenting style and school performance