Durable press cotton fabrics are treated to improve their re

\"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 some fabric specimens:

Solution

(I) Let mu1 be the mean for Permafresh

Let mu2 be the mean for Hylite

The test hypothesis:

Ho: mu1=mu2 (i.e. null hypothesis)

Ha: mu1 not equal to mu2 (i.e. alternative hypothesis)

The test statistic is

t=(xbar1-xbar2)/sqrt(s1^2/n1+s2^2/n2)

=-6.296

The p-value= 0.0002 (from student t table)

Assume that the significant level a=0.05

Since the p-value is less than 0.05, we reject the null hypothesis.

Answer: A. Yes.

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(II) Answer: B. Hylite