Question

"Durable press" cotton fabrics are treated to improve their recovery from wrinkles after washing "Wrinkle recovery angle" measures how well a fabric recovers from wrinkles. Higher is better. Here are data on the wrinkle recovery angle (in degrees) for the some fabric specimens.

Permafresh Hylite

124 147

104 199

142   149

111 156

123

A consumer group suspects that there is a difference in recovery from wrinkles after waching. Specifically, they want to test the claim that there is a difference in recovery between using Permafresh and Hilite. To investigate this, they identified the mean recovery from wrinkles after washing by measuring the wrinkle recovery angle in degrees for a sample of fabrics using Permafresh, and a sample of fabrics using Hylite.

At the 5% level of significance, is there enough evidence to conclude that there is a difference in wrinkle recovery angle between Permafresh and Hylite?

It is often reasonable to conclude that measurements are normal in distribution. So it is reasonable to assume the population of wrinkle recovery angle is normal for both Permafresh and Hylite. Also assume that the data represents a SRS (simple random sample) of fabrics using Permafresh and Hylite.

Answer 1

Solution : Here concept of two independent samples t-test is used.

Note : In the test assumption of equal population variances is used.

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