Statistics Flashcards
Mann-Whitney U Test
one independent variable - two independent groups
one dependent variable - rank-ordered data
Wilcoxon Matched-Pairs Signed-Ranks Test
one independent variable - two correlated groups
one dependent variable - rank-ordered data
Kurskal-Wallis Test
one independent variable - two or more independent groups
one dependent variable - rank-ordered data
Mann-Whitney is the nonparametric version of ______
the t-test for independent samples
Wilcoxon is the nonparametric version of ________
the t-test for correlated samples
Kurskal-Wallis is the nonparametric version of ________
the one-way ANOVA
Parametric tests are measured on _____ & _____ scales.
interval & ratio
Nonparametric tests are measured on _______ & _______ scales.
nominal & ordinal
Type I error
investigator rejects a true null hypothesis
Type II error
investigator fails to reject a false null hypothesis
3 predictions of the Central Limit Theorem
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
formula for standard error of the mean
SEM = standard deviation / square root of N
variance
standard deviation squared
percentage of scores within one standard deviation
68
percentage of scores within two standard deviations
95
percentage of scores within three standard deviations
99
t-test
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
ANOVA
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
one-way ANOVA
used when a study includes one independent variable
factorial ANOVA
used when a study includes two or more independent variables
Cohen’s d
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
Eta squared
indicates the percent of variance in the outcome variable that is accounted for by variance in the treatment
Pearson r
data on both variables represents a continuous scale (interval or ratio data)
Spearman rho
both variables are ranks
Point biserial
one variable is a true dichotomy and the other is continuous
Biserial
one variable is an artificial dichotomy and the other is continuous
eta
the variables are both continuous and have a nonlinear relationship
external validity
the degree to which a study’s results can be generalized to other people, settings, conditions, etc.
internal validity
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
moderator variables
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
mediator variables
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
