2015 PEM Boards Stats Notes: Napo Flashcards Preview

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Flashcards in 2015 PEM Boards Stats Notes: Napo Deck (20):


- pick exposed and non exposed groups and compare their incidence of disease


retrospective cohort

-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 - 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

Relative Risk (same as cumulative incidence ratio): (risk=proportion) Unitless

= Proportion of disease in exposed/Proportion of disease in non exposed

= (a/a+b)/(c/c+d)

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

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 

- (parametric) 

-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