Flashcards in Power and Sample Size Deck (12)

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1

## How large a sample do I need

###
not too small bc if so it will be waste of money resources since you will not get anything out of that study

larger than necessary, study wastes resources

therefore must estimate power to determine sample size

2

## precision analysis

### estimate how large a sample is needed to produce a given level of precision at a fixed confidence level

3

## Two types of statistical error

###
Type 1 error (alpha)

Type 2 error (beta)

4

## Statistical power

### 1-beta; probability that the null hypothesis will be rejected when it is false

5

## Under Neyman-Pearson, alpha is

### set by investigator

6

## Under Neyman-Pearson, beta

### is estimated and will be determined by such characteristics as sample size, trait variance and effect size

7

## Power analysis applies to

###
all major types of epi data:

1. dichotomous (binary)

2. multiple categories

3. continuous

4. time-to-event (in this case, power will be a function of the number of events)

8

## as alpha decreases

###
so will the power. It will decrease

But beta increased

9

## given in a fixed sample size:

###
if alpha increases, beta decreases

if alpha decreases, beta increases

10

## without changing the null hypothesis, the only way to increase power while using a smaller alpha level is to increase sample size

###
increases precision

allows a smaller effect to be detected

11

## Factors affecting statistical power

###
Z = a standard normal random variable

μ1 = mean under HA

μ0 = mean under H0

σ = population standard deviation

Zα = critical value at significance level of α

n = sample size

12