Durable press\" cotton fabrics are treated to improve their recovery from wrinkl

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 same fabric specimens discussed in the previous exercise Permafresh Hylite 106 147 150 182 103 192 120 140 130 A manufacturer wants to know how large is the difference in mean wrinkle recovery angle. a. The mean and the standard deviation for the Permafresh are: Round to 3 decimal places. Round to 3 decimal places. b. The mean and the standard deviation for the Hylite are: Round to 3 decimal places. Round to 3 decimal places. c. The standard error is: SE Round to 3 decimal places. The critical value from the distribution for a confidence interval of 99% is: Use degrees of freedom of 3. Use Technology Round to 3 decimal places. d. Using the the answer from above (all rounded to 3 decimal places calculate by hand a 99% confidence interval for the difference in mean wrinkle recovery angle to Hint Round to 3 decimal places.

Explanation / Answer

The statistical software output for this problem is:

Summary statistics:

Two sample T confidence interval:
?1 : Mean of Permafresh
?2 : Mean of Hylite
?1 - ?2 : Difference between two means
(without pooled variances)

99% confidence interval results:

Hence,

a) Mean = 121.8

Standard deviation = 19.162

b) Mean = 165.25

Standard deviation = 25.604

c) SE = 15.406

Critical value = 5.841

d) 99% confidence interval:

(-43.45 - 5.841*15.406, -43.45 + 5.841*15.406)

-133.436 to 46.536

Column Mean Std. dev. Permafresh 121.8 19.162463 Hylite 165.25 25.604362

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