STAT

Question 1

What is NNT?

Answer 1

NNT= 1/ARR, where ARR=absolute risk reduction

NNT = 1 / [c/(c+d) - a/(a+b)]

Denominator’s positive because more should have the problem who were untreated (c) vs “diseased” who were treated (a)

Question 2

What is relative risk?

Answer 2

Ratio (i.e. fractional) probability of outcome in the exposed group vs. the probability of outcome in the nonexposed group

RR = (a/[a+b])/(c/[c+d])

Question 3

Sensitivity and Specificity do/do not vary with disease prevalence

Answer 3

Do NOT vary with disease prevalence

Whereas positive and negative predictive value do vary with disease prevalence

Question 4

What is a type 1 error?

Answer 4

Alpha error, “p-value”

The chances of finding a difference when there is none (like a false-positive result)

When you’re an alpha, you think you’re hot shit even when you’re not

Question 5

What is relative risk

Answer 5

Ratio (i.e. fractional) probability of outcome in the exposed group vs. the probability of outcome in the nonexposed group

RR = (a/[a+b])/(c/[c+d])

Question 6

What is the power of a statistical test?

Answer 6

The “power” of your study is essentially how likely are your results to be correct

Power = 1 - beta error

Type 2 (beta) is chances of saying there’s no difference when there actually is

Question 7

What is the difference between relative risk and odds ratio?

Answer 7

The relative risk is how having an exposure affects your chances of an outcome compared to its frequency in the non-exposed

Odds ratio is the ODDS that the outcome will happen in the exposed group compared to the odds of it happening in the control group

They are the same when the prevalence of the outcome is low

Question 8

Which diagnostic test is affected by prevalence

Answer 8

For a given test, when there is increased prevalence of disease, the positive predictive value will increase
and the negative predictive value will decrease.

Sensitivity and specificity are independent of prevalence.

Question 9

Describe the different categories of translational research:

Answer 9

• T1: translating biomedical science to clinical efficacy knowledge
• T2: translating clinical efficacy knowledge to clinical effectiveness knowledge

T3: translating clinical effectiveness knowledge to improved health care quality and value and public
health’ (*improve individual patient outcomes
and public health)