Stats

Question 1

Probs vs odds

Answer 1

Probs= events over total
Odds= events over non

Question 2

Relative risks

Odds ratio

Answer 2

RR= (a over a plus b)/(C / C + d)
Odds ratio= ad/cb

RR is probability of the disease in the exposed over the probability of the disease in the non exposed

Odds ratio is the odd of exposure in the diseased over the odds of the exposure in the non disease

Question 3

RR and OR findings

Answer 3

Greater than one means there is a positive Association like smoking and COPD

Equal to one means there is no association

Less than one means there is a negative association such as smoking and ulcerative colitis

Question 4

Nnt

Nnh

Answer 4

Nnt is one over arr
Nnh is one over ar

Arr is (c over c plus d)- (a / a + b)
Ar is (a / A + B) - (C / C + d)

Question 5

Rrr

Answer 5

1-rr

Question 6

Bias from subject

Answer 6

Recall
Hawthorne

Solution
Blinding

Question 7

Bias from researcher

Answer 7

Observation
Selection

Solutions
Randomizing
Double blinding

Question 8

Bias from study

Answer 8

Counfounding: ice cream, drowning, summer. Third factor cancels out association

Effect modification: ocp, dvt, smoking. Third factor enhances association

Question 9

Precise vs accurate

Answer 9

Accurate is in the bullseye

Precise stays together