Risk (Stevens)

Question 1

(Absolute) Risk

Answer 1

Proportion of people who experienced a given outcome

Question 2

Relative Risk

Answer 2

Treatment Risk/Control Risk

Question 3

Relative Risk Reduction

Answer 3

Intermediate estimate of risk reduction

(Control Risk - Treatment Risk)/(Control Risk)

Question 4

Absolute Risk Reduction

Answer 4

Control Risk - Treatment Risk

Most conservative estimate of risk reduction (SMALL)

Question 5

Number Needed to Treat (to get positive outcome)

Answer 5

1/Absolute Risk Reduction

Question 6

Odds (in favor of patient living)

Answer 6

Note: this is within a single treatment, looking at whether patients live or die

(# pts living within treatment)/(# pts NOT living within treatment)

Question 7

Odds Ratio of dying

Answer 7

Least conservative estimate of risk reduction (BIGGEST: “this treatment really lowers your risk!”…but not really)

(Treatment Odds of dying)/(Control Odds of dying)

Question 8

Type I error

Alpha

Answer 8

Risk of randomly finding effect that is not actually there

False positive

“Statistical significance”

Question 9

Type II error

Beta

Answer 9

Risk of randomly NOT finding an effect that is actually there

False negative

“Power” (1 - Type II error)

Question 10

Systematic error

Answer 10

Due to bias, confounding, study design issues

Question 11

Random error

Answer 11

Due to chance alone (Type I error and Type II error)