# Kraushar Flashcards

2 X 2 tables for hypothesis testing:

(alpha, beta, and power)

Cumulative Incidence Definition and Equation:

**(new cases) / (total population at risk over time)**

- fraction of people initially free of the outcome but who develop it over a period of time

Null Hypothesis (Ho):

- states that there is no difference

Absolute risk difference =

I_{exposed} - I_{unexposed}

- incidence in exposed group minus incidence in unexposed group

Incidence equation in steady state:

**prevalence / duration**

Relative risk =

I_{exposed} / I_{unexposed}

- incidence in exposed group divided by incidence in unexposed group

Odds ratio definition and table:

- retrospective
- start with people who have disease, and go backwards to find risk factor

Duration equation in steady state:

**prevalence / incidence**

Prevalence equation in steady state:

**(incidence) X (average duration)**

2 X 2 tables for hypothesis testing:

(type 1 and 2 errors)

The probability of two mutually exclusive events, A or B, occurring =

**(probability A) + (probability B)**

Type II error:

- FALSE NEGATIVE
- saying there is no difference in treatment effects when there is.
- failing to reject (accepting) the null hypothesis when it should be rejected

power =

**1 - beta**

- power of study to pick up a difference when it actually does exist

Incidence Rate definition and equation:

**(new cases) / (total time lapsed)**

- rate at which new disease has occurred in the population at risk per some unit time

Normal distribution:

- classic bell curve
- highest density in middle, tapers off on both sides
- mean, median, and mode all in the same place (dead center of bell curve)
- dead center for all these = perfect normal distribution (Gaussian)

2 X 2 tables for hypothesis testing:

(false hits and false misses)