Biostat

Question 1

How do you calculate NNH?

Answer 1

NNH = 1/Attributable risk

ARI = risk exposed - risk nonexposed

Question 2

How do you calculate Odds Ratio?

Answer 2

OR = (AD)/(BC)

Question 3

What statistical parameter is defined as the probability of a given test result occurring in a patient with a disorder compared to the probability of the same result occurring in a patient without the disorder

Answer 3

Likelihood ratio

Question 4

How do you calculate attributable risk percent?

Answer 4

Attributable risk percent (ARP) =
1. (exposed risk-unexposed risk)/exposed risk

2. (RR-1)/RR

Question 5

How is population attributable risk percent calculated?

ie percentage of stroke in population attributable to smoking

Answer 5

PARP = (risk in total pop - risk in unexposed)/risk in total pop

Question 6

What is the best statistical approach to evaluate the relationship between a quantitative dependent variable and independent variable of interest while controlling for effects of other factors (adjustment variables)

Answer 6

Multiple linear regression

Question 7

How is positive predictive value (PPV) calculated from Specificity and sensitivity

Answer 7

PPV = TP/(TP+FP)

Sensitivty = TP/(TP+FN)
Specificity = TN/(TN+FP)

Question 8

How do you calculate Number needed to treat?

Answer 8

NNT = 1/ARR

Question 9

What does the kappa statistic describe?

Answer 9

inter-rater reliability

range from -1 to +1

Question 10

What is it called when you repeat primary analysis calculations after modifying certain criteria or variable ranges?

Answer 10

Sensitivity analysis

Question 11

What is the type of study design called that utilizes >/= 2 interventions and all combinations of these interventions

Answer 11

Factorial study design

Question 12

What kind of bias occurs when the survival benefits of a screen test are overstated due to the detection of a disproportionate number of slowly progressive, benign cases

Answer 12

Length-time bias