USING G*POWER SOFTWARE (Calculating Power) BIOSTATS

PART 1

Step-by-Step Guide to Assignment 2.1

Using the same data, PUBH8500_Week01_dataset.sav, you used in the Discussion Question from Week 1 and the related descriptive statistics from the Week 1 Assignment complete the following:

1. Calculate the minimum sample size you will need (using manual calculations) to conduct a t test to determine if the difference in age in people with and without hypertension is significant. Use the standard deviation for age calculated in week 1. Assume a 2-tailed test with alpha = .05 and Power = 80% and that the difference you expect to observe between the 2 groups is 5 years.

NOTE: This guide will use Practice_Week01_dataset.sav

Step 1. The t test is used to compare two group means. The formula for sample size for a two-tailed test comparing two independent means is:

n = 2σ2 (Z1-β + Z 1-α/2)2 / (amount of difference)2

Z1-β = 0.84

Z 1-α/2 = 1.96

From the descriptive statistics in Week 1 practice application,

Std. dev. (σ) for age = 7.735

Thus, σ2 = 59.83

The expected amount of difference = 5 years

(The amount of difference)2 = 25

Given the above,

n = 2(59.83) (0.84 + 1.96)2 / 25

= 119.66 * 7.84 / 25

= 37.53

= 38 participants are needed per group; in total 76 participants are needed