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MAT 155 Lab 6

Sections 7.1-4Estimating Population Proportion and Mean

Team #___ Members: (1)______(2)______

(3)______(4)______

Date______Student’s Name______Sec. #_____ Score______

Lab6EstimatingPropMean.doc

1.In a Gallup poll, 491 randomly selected adults were asked whether they are in favor of the death penalty for a person convicted of murder, and 65% of them said that they were in favor.

a. Find the point estimate of the percentage of adults who are in favor of this death penalty.

b. Find a 95% confidence interval estimate of the percentage of adults who are in favor of this death penalty.

c. Can we safely conclude that the majority of adults are in favor of this death penalty? Explain your answer.

2.As a manufacturer of golf equipment, the Spalding Corporation wants to estimate the proportion of golfers who are left-handed. (The company can use this information in planning for the number of right-handed and left-handed sets of golf clubs to make.) How many golfers must be surveyed if we want 99% confidence that the sample proportion has a margin of error of 0.025?

a. Assume that there is no available information that could be used as an estimate of.

b. Assume that we have an estimate of found from a previous study that suggests that 15% of golfers are left-handed (Based on a USA Today report).

c. Assume that instead of randomly selected golfers, the sample data are obtained by asking TV viewersof the golfing channel to call an “800” phone number to report whether they are left-handed or right-handed. How are the results affected?

3.In order to help identify baby growth patterns that are unusual, we need to construct a confidence interval estimate of the mean head circumference of all babies that are two months old. From a random sample of 100 babies the mean head circumference is 40.6 cm. Assuming that the population standard deviation is known to be 1.6 cm, find a 99% confidence interval estimate of the mean circumference of all two-month-old babies. What aspect of this problem is not realistic?

4.The Tyco Video Game Corporation finds that it is losing income because of slugs used in its video games. The machines must be adjusted to accept coins only if they fall within set limits. In order to set those limits, the mean weight of quarters in circulation must be estimated. A sample of quarters will be weighed in order to determine the mean. How many quarters must we randomly select and weigh if we want to be 90% confident that the sample mean is within 0.025 g of the true population mean for all quarter? Use the standard deviation (rounded to three-significant digits) from the sample of quarters in Data Set 29 (in Appendix B) as an estimate for the population standard deviation.

5.Refer to Data Set 1 in Appendix B and use the sample data to complete the following.

a. Construct a 99% confidence interval estimate of the mean body mass index for men.

b. Construct a 99% confidence interval estimate of the mean body mass index for women.

c. Compare and interpret the results. We know that men have a mean weight that is greater than the mean for women, but do men also have a mean body mass index that is greater than the mean body mass index of women?

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