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43 Cards in this Set
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Parametric Statistical Tests

Used for dependent variables measured on an interval or ratio scale
Dependent variable data must be continuous and normally distributed Examples: Student's ttest Paired ttest ANOVA, ANCOVA Repeated measures Analysis of Variance 

OneTailed Test

A research hypothesis that one group will be higher/lower than another (directional)


TwoTailed Test

A research hypothesis that one group will be different than another (nondirectional)


What is the advantage of a Twotailed test?

They are easier to reject the null hypothesis


What are the disadvantages of a twotailed test?

Can lead to Type III error


What is Type III error?

There is a statistically significant difference between the gps, but the direction of the difference stated by the researchers based on their sample data is incorrect


What is an Independent Group?

Different subjects in each gp being compared (groups are mutually exclusive)
Comparisons are made between groups Examples: Parallel designs, M vs FM, MSII vs. MSIII 

What is a dependent group?

The subjects in each group being compared are the same.
Comparisons are made within a group or cohort at different points in time. Examples: PretestPosttest, BeforeAfter, Crossover designs 

What is a student's ttest?

Test used to compare 2 independent groups for differences on an interval or ratio level dependent variable
Commonly used to compare characteristics of 2 tx groups at beginning of a study (to see if gps were equal at baseline) or outcomes at end of study (determine the effect of a tx) 

What is a paired ttest?

Same as a student's ttest, but the two groups are dependent
Often used in before/after, pretest/posttest, and crossover studies 

What is Analysis of variance (ANOVA)?

Test used to compare 3 or more independent groups for differences on an interval or ratio level dependent variable
Used to compare treatment gps at both the beginning of a study (to test for equality) and at the end of a study (to test for effectiveness) 

Why is it better to use ANOVA than ttests for large studies?

ANOVA=1 possibility
ttests=need to use multiple tests leading to many possiblities 

What are the types of ANOVA tests?

Oneway (1 IV, 1 DV)
Twoway (2 IV, 1 DV) MANOVA (>1 IV, > 1 DV) 

In ANOVA posthot tests, p < alpha tells you what?

Does not tell you which groups are different from each other.


What is Repeated measures ANOVA?

Similar to ANOVA, but for 3 or more dependent groups
Abaseline vs. Atime1 vs Atime2 vs... 

What is analysis of Covariance (ANCOVA)?

Tests for differences between gps in interval or ratio data, but also controls for differences between the gps in terms of covariates/confounding variables
May be used regardless of number of gps compared, or the relationship between the groups (independent, dependent) 

What are NonParametric statistical tests?

Statistical tests used when dependent variables are measured on a nominal or ordinal scale
Also used when data from interval or ratio scale dependent variables are not normally distributed Examples: Chisquare, Friedman 

What is a Chisquare test?

Measures differences in proportions (percentages) between groups
Differences are between independent groups on a nominal level data Commonly used to analyze contingency tables which can be used to determine equality of gps at baseline or differences between gps after treatment Sample size should always be atleast an expected frequency of 5 subjects per data cell 

What if there are less than five subjects per cell?

Fisher's Exact Test


What is McNemar's Test?

Similar to Chisquare, but for paired or matched data (dependent)


What is the MantelHaenszel Test?

Similar to Chisquare, but for stratified data
One contigency table for each level of stratification 

What is the MannWhitney U Test?

Analogous to the student's ttest, but dependent variable is ordinal or not normally distributed


What is the Wilcoxon SignedRank?

Analogous to paired ttest, but dependent variable is ordinal or not normally distributed


What is the KruskallWallis test?

Analogous to ANOVA, but dependent variable is ordinal or not normally distributed


What is the Friedman test?

Analogous to repeated measures ANOVA, but dependent variable is ordinal or not normally distributed


What is the KaplanMeier Survival Analysis?

A nonparametric test used to examine differences in the probability of an event occurring between treatment groups over time


What is the logrank test?

Used to determine if the differences in probabilities between the groups are different over the entire time of the study


What is Pearson's r (aka Correlation Coefficient)?

Measures degree of relationship between two continuous variables
Data must be interval or ratio Values for r range from 1 to +1 1=perfect negative relationship 0=no relationship +1=perfect positive relationship Both p value and the test statistic (r) are needed to interpret result. Look at p value first. If p < alpha, then interpret the r value 

What is Spearman's rho?

Similar to Pearson's r, but with ordinal (ranked) data


What is regression analysis?

Derives an equation that allows researchers to predict a value for a dependent variable given one or more independent variables
Dependent variable usually measured on an interval or ratio scale. 

What if the dependent variable is ordinal or nominal in regression analysis?

Use logistic regreesion


What is the regression equation?

y=mx+b


What is regression weights (m)

How much each individual IV(x) contributes to the regression equation (unstandardized)


What is Beta (1  +1 scale)?

Standardized regression wt. allows reader to assess the strength of each IV(x) in predicting the DV (y)


What is r^2 (01 scale)?

Total amount of variance (%) explained by the combo of all IVs included in the analysis (01)


What is the Cox Proportional Hazard Model?

Uses regression analysis to predict for each subject the time to the study end point (e.g. death)
While controlling for time and confounding variables, the Cox regression equation slop coefficients (m) can be translated into relative risk values for the end point for each level of the independent variable. 

What is Relative Risk (aka hazard ratio)?

Measure of the relative frequency of an event when a specific factor is present


What is the relative risk equation?

Incidence rate of event among those exposed to a specific factor / "" those not exposed to the factor (control)


How is incidence calculated?

# who experience event / total # at risk


What sudy design should Relative risk only be used in?

Prospective study designs


How is the relative risk measured?

RR=1: variables are independent (no relationship)
RR<1: those exposed have lower incidence of event than those not exposed RR>1: those exposed have higher incidence of event than those not exposed 

How are confidence intervals used with relative risk?

Determination of statistical significance (instead of p values)
Always look at the CI before interpreting the RR 

What type of studies are Odds ratios used for?

Retrospective study
