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The standard deviation of the weights of elephants is known to be approximately 20 pounds. We wish to construct a 98% confidence interval for the mean weight of newborn elephant calves. Eighty newborn elephants are weighed. The sample mean is 275 pounds. The sample standard deviation is 16 pounds. What is the best point estimate of the population mean?

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Related textbook solutions

Introductory Statistics
OER Edition, 2013
Openstax
ISBN: 9781938168208

Related questions

A simple random sample of size n is drawn from a population that is known to be normally distributed. The sample mean,Ā xĀÆ\bar{x}Ė‰, is determined to be 104.3 and the sample standard deviation, s, is determined to be 15.9. (a) Construct the 90% confidence interval for the population mean if the sample size, n, is 15. (b) Construct the 90% confidence interval for the population mean if the sample size, n, is 25. How does increasing the sample size affect the width of the interval? (c) Construct the 95% confidence interval for the population mean if the sample size, n, is 15. Compare the results to those obtained in part (a). How does increasing the level of confidence affect the confidence interval? (d) Construct the 90% confidence interval for the population standard deviation if the sample size, n, is 15.

Ā 

6. As the test statistic becomes larger, the p-value

(a) gets smaller

(b) becomes largerĀ 

(c) stays the same, since the sample size has not been changed

(d) becomes negative.

Ā 

7. To describe the sampling distribution of the sample proportion, we use

(a) The sample proportionĀ 

(b) The population proportionĀ 

(c) The population mean

(d) The population mean

Ā 

8. When small samples are used to estimate a population mean, in cases where the population standard deviation is unknown and the original distribution is normal:

(a) There always will be a large amount of sampling error.

(b) the t-distribution must be used to obtain the critical value.

(c) the resulting margin of error for a confidence interval estimate will tend to be fairly small.

(d) the z distribution must be used to obtain the critical value.

Ā 

Ā 

Costco Customer Satisfaction. Consumer Reports uses a 100-point customer satisfaction score to rate the nation's major chain stores. Assume that from past experience with the satisfaction rating score, a population standard deviation of is expected. In 2012, Costco, with its 432 warehouses in 40 states, was the only chain store to earn an outstanding rating for overall quality. A sample of 15 Cosco customer satisfaction scores follows.

95Ā  Ā 90Ā  Ā 83Ā  Ā 75Ā  Ā 95Ā  Ā 98Ā  Ā 80Ā  Ā 83Ā  Ā 82Ā  Ā 93Ā  Ā 86Ā  Ā 80Ā  Ā 94Ā  Ā 64Ā  Ā 62

a. What is the sample mean customer satisfaction score for Costco?

b. What is the sample variance?

c. What is the sampleĀ standard deviation?

Construct a hypothesis test to determine whether the population standard deviation of should be rejected for Costco. With a.05 level of significance, what is your conclusion?

Ā 

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