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EBM Exam 1
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Type of data in non-parametric tests
nominal
ordinal
Nominal data
mutually exclusive
yes/no
male/female
Chi squared test
two samples
at least 40 observations (20 per group)
nominal data
Fisher's Exact
similar to chi squared but for smaller sample sizes
two groups
less than 5 per group
usually for uncommon events
for nominal data
Mantel-Haenszel
three or more groups
series of chi-squares
totals are added up and overall chi-square is calculated
for nominal data
McNemar's Test
similar to chi-squared
data is paired (there is a control or pt serves as their own control)
for nominal data
Ordinal Data
categorical
ranked on a scale with no consistent distance between values
ex. pain scale
Mann-Whitney U/Wilcoxon Rank Sum
two groups
ranks individual observations rather than values
data values are assigned from lowest to highest
the sum of the data is totalled at the bottem fo the chart
(rank pain 1-6 and the group with lower number has better pain control)
Kruskal-Wallis
for observational data
for multiple comparisons
if average ranks are close H
_{0}
is not rejected
post hock analysis needed to determine difference between treatment groups
Friedman's test is similar for 3 or more groups
Wilcoxon signed rank
similar to paired t-test
for paired data
differences arranged in order of absolute value
observations of 0 are excluded
average rank is assigned
continuous data
ratio or interval data
placed on a numerical scale with infinite amount of values
equal distance between those values
T-test
"student's T-test"
compares the mean of a population to the known mean
2 groups
variance of both groups must be equal
interval or ratio data
ANOVA
for interval or ratio data
3 or more groups
ANCOVA
for ordinal or ratio data
similar to ANOVA but controls for covariates
ex. study effect of bisphosphonates on osteoprosis, but age and exercise are also factors, control for these to see the difference the drug makes
Paired T-test
for interval or ratio data
compare the mean difference between 2 groups that are paired or matched
can be used when the subject is their own control (cross over)
ANOVA for repeated measures
similar to ANOVA but measures subjects under a different set of conditions in a repeated manner
ex. pt with osteoporosis screened anually for next 5 years for changes in BMD
correlation
measure of association between 2 variables
r ranges from -1 to 1
independant variable is x
dependent variable is y
regression
0.9-1 = excellent correlation, probably predictive
0.7-0.9 = good correlation, may be predictive
0.6-0.7 = good correlation, may not be predictive
<0.6 considered not predictive
Kaplan Meier survival analysis
survival analysis as a function of time
interval or ratio data
time on the x axis
Survivial analysis censored vs. uncensored
censored means incomplete data, but is analagous to intent-to-treat
Post-Hoc Analyses
performed after primary analysis when H
_{0}
has been rejected
considered inferior to planned comparisons
often easier to understand
Author
Rx2013
ID
132680
Card Set
EBM Exam 1
Description
Biostats 3
Updated
2012-02-03T22:35:17Z
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