# Confidence interval, test of hypothesis

1. Post-It notepads have an unusual adhesive that must be strong enough to stick, but weak enough to not tear the paper when pulled to release. Several batches of adhesives were tested for consistency. Adhesiveness is measured in ounces per square inch (osi). Measurements from six batches of adhesives are given below. Assume the population of adhesiveness follows a normal distribution. (Values are rounded for your convenience.)

DATA: 87, 94, 96, 92 95 106

a. Construct the 98% confidence interval estimate for the true mean of this population using these data.

b. Interpret your confidence interval in the language of the problem. Include all four parts in your statement. (Re-read the problem.)

c. Calculate the sample median and third quartile. Include units.

median = _________, Q3 = ________

2. The manufacturer of a competitor to Post-It notepads claims that the mean time their product will maintain its ability to stick to a piece of paper is 92.0 hours. An experiment was conducted to test the competitors claim.

a. State the hypotheses for this test using appropriate symbols.

Ho:

Ha:

b. The population of the individual "stick times" is skewed to the right due the effect of humidity and other environmental conditions. None of the parameter values for this population are known.

Does the original population follow the normal distribution? Yes or No. _________

c. A sample of 40 items will be tested and the average time calculated.

Is it reasonable to say the population of all possible x-bar values follows a normal distribution?

Answer Yes or No; then state briefly why you selected your answer. _________

d. In a sample of 44 items the mean time that the product stuck was 86.2 hours with a standard deviation of 19.0 hours. Construct a 95% confidence interval for the true mean.

Show all of your work. (A statement in the language of the problem is not needed.)

Decision: "Reject Ho" or "Do not reject Ho." ________________________ .

Conclusion in the language of the problem:

(Be sure to include all four parts.)

#### Solution Summary

Answers questions on confidence interval, sample median, third quartile, test of hypothesis, true mean etc.