2015 PEM Boards Stats Notes: Napo

Question 1

Cohort

Answer 1

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

Question 2

retrospective cohort

Answer 2

-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

Question 3

ANOVA ??? MANOVA ???

Answer 3

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

Question 4

Wilcoxan Rank Sum test ???

Answer 4

• compares the MEDIANS of two independent populations with non-parametric data

Question 5

Mann-Whitney U test ???

Answer 5

• Used for comparing the MEANS of two independent groups that are nonparametric

Question 6

Kruskal Wallis Test ???

Answer 6

• used for THREE or more independent groups with data that is assumed to be non-parametric

Question 7

Student’s t test ??? Paired t test ???

Answer 7

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)

Question 8

Chi square & Fisher’s Exact test ???

Answer 8

• comparison of proportions of two groups of categorical variables -if > 5 measurements → Chi square -if <5 measurements → Fisher Exact

Question 9

Kolmogorov-Smirnov & Shapiro-Wilk ???

Answer 9

• tests to determine whether data have a normal distribution

Question 10

case-control study ???

Answer 10

-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

Question 11

case series ???

Answer 11

is a descriptive study which describes a group of patients with the same disease process

Question 12

Prevalence

Answer 12

-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

Question 13

Incidence

Answer 13

-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

Question 14

Relative Risk

Answer 14

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

Question 15

Odds ratio

Answer 15

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

Question 16

Mann Whitney U test / Wilcoxon rank-sum test/ Wilcoxon signed-rank test

Answer 16

• (nonparametric)
• 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

Question 17

Students t test

Answer 17

• (parametric)
• Comparison of mean for a continuous variable
• Change in cholesterol level between two groups randomized to two different medications

Question 18

Analysis of variance (ANOVA)

Answer 18

• (parametric)
• 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

Question 19

Pearson coefficient of correlation

Answer 19

• (parametric)
• Measurement of degree of association or strength of linear relationship between two variables that are continuous
• Relationship between immunization rate and infant mortality rate

Question 20

Spearman rank correlation

Answer 20

• (nonparametric)
• 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