12. Biostatistics Flashcards
Define “parametric tests” and give examples
Interval or ratio data; tests hypothesis in NORMALLY distributed population. MORE POWER.
Examples of parametric tests
t-test; ANOVA; Pearson Coefficient; Multiple Regression
Define “non-parametric tests” and give examples
Data from a SKEWED distribution; LESS POWER
Examples of non-parametric tests
Chi-Square; Logistic regression; Spearman Rho; Wilcoxon Signed Rank
Define “degrees of freedom”
of pieces of info that can vary independently from one another; n -1, where n is # of cases in the sample
One-tailed t-test
Used when direction of difference is known or postulated
Two-tailed t-test
Used when direction of difference is unknown or not postulated
Paired t-test
BEFORE & AFTER tests of SAME GROUP; Pre & Post test analysis
Independent t-test
Most common statistical method; Simple (yet powerful); Comparison between control and test group. ONLY TWO GROUPS CAN BE COMPARED. Assumes normal distribution. AKA = two-sample t-test; tests DIFFERENT GROUPS
Analysis of Variance (ANOVA)
Accepted method of comparing TWO OR MORE groups from ONE STUDY; determines RELATIONSHIP BETWEEN IV & DV; Test statistic is an F RATIO. Variables are factors.
Post-hoc tests
Defines which of 3 or more groups are actually different; test after ANOVA to detemine what the significance actually is
Tukey
Post-hoc test; Used when larger number of comparisons are made; assumes groups are of equal size; Used to determine which means are significantly different
Dunn
Post-hoc test; Used when only a few comparisons are made
Bonferroni
Post-hoc test; Used when 5 or less comparisons are made
Repeated Measures ANOVA
Used when experiment involves matched subjects; Measure an outcome in each subject before, during, and after intervention
Analysis of Covariance (ANCOVA)
Enables testing of differences among at least 3 groups, while adjusting for effects of covariates or confounders on DV
MANOVA
Used when 2 DVs are assessed
Chi-Square Test
Non-parametric; applied to non-normally distributed populations; “Goodness of Fit test”or “Pearson Chi Square”; Statistically significant difference between observed (actual) frequencies and expected frequency of variables; Answers research questions about RATES, PROPORTIONS, OR FREQUENCIES. GREATER CHI SQUARE, LESS LIKELY DIFFERENCE IS D/T CHANCE
Fisher’s Exact Test
Non-parametric test for nominal data. Used instead of Chi Square in VERY SMALL SAMPLE SIZE
McNemar’s Test
Non-parametric test for nominal data from PAIRED SAMPLES
Mantel-Haenszel
Non-parametric test for nominal data to control for effects of a confounder.
Mann-Whitney U Test
Non-parametric test for ordinal variables; OFTEN USED TO COMPARE SURVIVAL CURVES
Wilcoxon Rank Signed Test
Non-parametric equivalent of PAIRED T-TEST for ORDINAL variables. Use with 2 correlated samples (before & after) or difference between 2 groups.
Kruskal-Wallis test
Non-parametric equivalent of ANOVA to compare ? 3 groups of different groups with ordinal data
