Unit 6

T-test for independent samples

The t-test is a test difference between two independent groups. The means are compared Mean 1 against the Mean 2.

When do we use the t-test for independent samples?

When we compare the means of two independent groups.

When the data are expressed in interval and ratio.

When the sample is less than 30.

F-Test

The F-test (ANOVA- Analysis of Variance) is another parametric test used to compare the meansof three or more groups of independent samples.

Why do we use F-test? Because we want to find out if there is a significant difference between and among the means of three or more independent groups.

A B C

8 14 10

7 16 12

9 12 16

13 17 15

10 11 12

Exercise

In an experiment to determine the germicidal effect of 3 brands of bath soap, 5 groups of nursing students were randomly assigned to each of the 3 popular brands of soap: Brand A, B, and C. Bacterial count after 1 hour of using the soap was recorded as shown in table1. Find if there’s a significant difference (5% level) among the different brands of soap using ANOVA.

BRAND