Biostats 3 & 4 Flashcards
What are different testing methods for categorical data
Chi2
Fisher’s exact
What are the rules and assumptions of categorical data
data are arranged into categories
data are independent; random sample from the population
must be a positive integer >0
What are the types of studies for categorical data
cross sectional prospective retrospective experimental diagnostic test
What is a cross sectional study
recruit study group and define two categories
What is a prospective study
recruit group with some difference and follow them
What is a retrospective study
start with a condition and look backwards at potential causes
What is an experimental study
recruit a group, manipulate variables
What is a diagnostic test
positive and negative results
When will a fisher’s exact test be used over chi2
when a sample group is <5
What are the degrees of freedom
of variables in final calculation that are free to vary
How is DOF calculated
usually n-1
df=(rows-1) X (columns-1)
What is the use of Chi2
tests the goodness of fit; observed frequency compared to theoretical
What does a student/paired t-test compare
means of 2 groups
What are the requirements and assumptions of T-tests
n>30 for each population
data is continuous
data is a random sample and normally distributed
each population should have the same variance
WHat are the different types of t tests
one sample t test
independent t test
dependent t test
What is a one sample t test
compare a group’s mean to a benchmark group
What is an independent t test
compare 2 independent groups
What is a dependent t test
compare 2 groups that are somehow related
When do you use a 1-tailed t test
population is significantly greater than the other
When do you use a 2-tailed t test
population is significantly different from the other population
What is the use of ANOVA
to compare the means of 3 or more groups
What are the rules and assumptions of ANOVA
compares all groups at once
tell you there is a difference between at least 2 groups
examines variance from mean scores
takes deviation for mean, square and sum= sum of squares
independent observations
normally distributed data
homogeneity of variance
What is needed after ANOVA
post-hoc test
WHat are the types of post hoc tests
Turkey test
Dunnett’s
What is a Turkey post hoc test
compares each group to every other group
What is a Dunnett’s post hoc test
compares all groups to a control group
What are the nonparametric tests
Mann Whitney U test
Wilcoxon Signed ranks
Kruskal Wallis
What does a Mann Whitney U test measure
RANKS instead of actual values
What does a WIlcoxon Signed Rank test measure
absolute values of differences are sorted and ranked
WHat is the alternative for independent t-test if there is skewed data
mann-whitney u test
What is the alternative for dependent t-test if there is skewed data
wilcoxon signed ranks
What is the alternative for ANOVA if there is skewed data
Kruskal Wallis
Do you still need a post hoc test with a Kruskal Wallis
yes
When is a box and whisker plot used
not a normal distribution
