- pick exposed and non exposed groups and compare their incidence of disease
-examines two groups with different exposures and compares their outcomes retrospectively usually by chart review -the exposure outcome would have already occurred at the time of the study and the data is collected after-the-fact
ANOVA ??? MANOVA ???
ANOVA - used to compare the means of 3 or more independent groups with a single dependent variable (parametric data) MANOVA - more than one dependent variable and when 3 or more independent groups
Wilcoxan Rank Sum test ???
- compares the MEDIANS of two independent populations with non-parametric data
Mann-Whitney U test ???
- Used for comparing the MEANS of two independent groups that are nonparametric
Kruskal Wallis Test ???
- used for THREE or more independent groups with data that is assumed to be non-parametric
Student’s t test ??? Paired t test ???
Student’s t test - compares the means of 2 sets of continuous data that have a normal distribution Paired t test - groups are paired (ie before and after an intervention)
Chi square & Fisher’s Exact test ???
- comparison of proportions of two groups of categorical variables -if > 5 measurements → Chi square -if <5 measurements → Fisher Exact
Kolmogorov-Smirnov & Shapiro-Wilk ???
- tests to determine whether data have a normal distribution
case-control study ???
-is an observational analytic study following subjects on the basis of whether they do or do not have a disease to determine the possible effect of an exposure
case series ???
is a descriptive study which describes a group of patients with the same disease process
-equals the number of existing cases of a disease for a total population at a given point in time -rate of disease at any one point in time that includes new and old cases
-rate of new cases of a certain disease at any one point in time -measurement of the instantaneous rate of developing a disease in a population and equals the number of new cases of disease in a given time period over the total person – time of observation
Relative Risk (same as cumulative incidence ratio): (risk=proportion) Unitless
= Proportion of disease in exposed/Proportion of disease in non exposed
In words, if RR=2 then the exposed are 2 times more likely to develop disease than the nonexposed.
Lower limit is 0
Ratio of 1 means no association
Upper limit is infinity which depends on the incidence of the NONEXPOSED group
Odds ratio: (ratio=odds) Unitless
= Odds of disease among exposed/odds of disease among non exposed
= ratio of dz:no dz in exposed group/ratio of dz:no dz in non exposed group
= (a/b)/(c/d) = a*d/b*c
Mann Whitney U test / Wilcoxon rank-sum test/ Wilcoxon signed-rank test
-Comparison of median ranks for an ordinal type or continuous data
-ie. Difference in exam scores in two groups of students who were given computerized compared to paper exam format
Students t test
-Comparison of mean for a continuous variable
-Change in cholesterol level between two groups randomized to two different medications
Analysis of variance (ANOVA)
-Comparison of mean between more than two independent groups
-Difference in the white cell count in multiple groups of patients after diagnosed with a specific illness
Pearson coefficient of correlation
-Measurement of degree of association or strength of linear relationship between two variables that are continuous
-Relationship between immunization rate and infant mortality rate
Spearman rank correlation
-Measurement of degree of association between ranks of two variables (either both ordinal or one is ordinal and other is continuous)
-Relationship between height and weight in low birth weight babies over a time period