dif to remember

Question 1

positive likelihood ratios indicate

Answer 1

LR+ = sens / (1 - spec) = TP/FP –> probability of an individual with the condition having a positive test / probability of an individual without the condition having a positive test

Question 2

negative likelihood ratios indicate

Answer 2

LR- = (1-sensit) / specif) FN/TN–> probability of an individual with the condition having a negative test / probability of an individual without the condition having a negative test

Question 3

RRR - ex.

Answer 3

2% of patients who received flu shot develop the flu, while 8% of unvaccinated patients develop flu then RR=2/8 = 0.25
RRR=1-RR = 0.75

Question 4

Length time bias - example

Answer 4

a slowly progressive cancer is more likely detected by a screening test than a rapidly progressive test

Question 5

t-test vs ANOVA vs CHI-square according to action

Answer 5

t-test –> checks difference between means of 2 groups
ANOVA –> Checks differences between means of 3 or more groups
CHI-square –> Checks differences between 2 or more percentages or proportions of categorical outcomes (not mean values)

Question 6

Hawthorne effect

Answer 6

(aka observer effect) is the tendency of study subjects to change their behavior as a result of their awareness that their being studied

Question 7

Fisher’s exact test

Answer 7

like X square test but in smaller sample

less than 10 people in each cell

Question 8

1. crude birth rate

2. crude mortality

Answer 8

1. number of live birth / total population

2. number of live death / total population

Question 9

factorial design

Answer 9

studies involve randomization to different interventions with additional study of 2 or more variables

Question 10

attrition bias - type and definition

Answer 10

selection bias
- significant loss of study participants may cause bias if those lost to follow up differ significantly from remaining subjects

Question 11

prevalence (Neyman) bias - type and definition

Answer 11

selection bias

- exposure that happen before disease assessment can cause study to miss diseased patients that die early or recover

Question 12

ascertainment (sampling) bias - type and definition

Answer 12

selection

study population differ from target population due to nonradom selection method

Question 13

reporting bias - type and definition

Answer 13

observational

- subjects over or under report exposure history due to perceived social stigmatization

Question 14

Surveillance (detection) bias - type and definition

Answer 14

observational
- risk factor itself causes increased monitoring in exposed group relative to unexposed group, which increases probability of identifying a disease