Suppose that a random sample of 50 bottles of a particular brand of cough syrup is selected and the alcohol content of each bottle is determined. Let u denote the average alcohol content for the population of all bottl resulting 95% confidence interval is (7.8, 9.6). (a) Would a 90% confidence interval calculated from this same sample have been narrower or wider than the given interval? Explain your reasoning. • The 90% would be narrower since the z critical value for 90% is smaller than the z critical value for 95%. O The 90% would be the same since the z critical value for 90% is the same as the z critical value for 95%. O The 90% would be wider since the z critical value for 90% is larger than the z critical value for 95%. O The 90% would be wider since the z critical value for 90% is smaller than the z critical value for 95%. O The 90% would be narrower since the z critical value for 90% is larger than the z critical value for 95%. (b) Consider the following statement: There is a 95% chance that u is between 7.8 and 9.6. Is this statement correct? Why or why not? O It is not a correct statement. We are 95% confident in the general procedure for creating the interval, but the mean may or may not be enclosed in this interval. O It is not a correct statement. There is a 5% chance that the mean is between these values. O It is not a correct statement. Each interval contains the mean by definition. O It is a correct statement. Each interval contains the mean by definition. O It is a correct statement. There is only a 5% chance that the mean is not between these values.

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The answers are given as shown. Please show the steps needed to arrive at (c) and (d). Thanks!

Suppose that a random sample of 50 bottles of a particular brand of cough syrup
resulting 95% confidence interval is (7.8, 9.6).
selected and the alcohol content of each bottle is determined. Let u denote the average alcohol content for the population of all bottles of the brand under study. Suppose that the
(a) Would a 90% confidence interval calculated from this same sample have been narrower or wider than the given interval? Explain your reasoning.
O The 90% would be narrower since the z critical value for 90% is smaller than the z critical value for 95%.
O The 90% would be the same since the z critical value for 90% is the same as the z critical value for 95%.
O The 90% would be wider since the z critical value for 90% is larger than the z critical value for 95%.
O The 90% would be wider since the z critical value for 90% is smaller than the z critical value for 95%.
O The 90% would be narrower since the z critical value for 90% is larger than the z critical value for 95%.
(b) Consider the following statement: There is a 95% chance that u is between 7.8 and 9.6. Is this statement correct? Why or why not?
O It is not a correct statement. We are 95% confident in the general procedure for creating the interval, but the mean may or may not be enclosed in this
interval.
O It is not a correct statement. There is a 5% chance that the mean is between these values.
O It is not a correct statement. Each interval contains the mean by definition.
O It is a correct statement. Each interval contains the mean by definition.
O It is a correct statement. There is only a 5% chance that the mean is not between these values.
(c) Consider the following statement: We can be highly confident that 95% of all bottles of this type of cough syrup have an alcohol content that is between 7.8 and 9.6. Is this statement correct? Why or why not?
O It is not a correct statement. The interval is an estimate for the sample mean, not a boundary for sample values.
O It is a correct statement. This is the definition of a confidence interval.
O It is not a correct statement. The interval is an estimate for the population mean, not a boundary for population values.
O It is a correct statement. This interval is a great estimate of boundaries for population values.
O t is not a correct statement. The interval is an estimate for the sample mean, not a boundary for population values.
(d) Consider the following statement: If the process of selecting a sample of size 50 and then computing the corresponding 95% interval is repeated 100 times, s95 of the resulting intervals will include u. Is this statement correct? Why or why not?
O It is not a correct statement. We expect 95 out of 100 intervals will contain the mean, but we don't know this to be true.
O t is a correct statement. This is guaranteed by the definition of confidence interval.
Transcribed Image Text:Suppose that a random sample of 50 bottles of a particular brand of cough syrup resulting 95% confidence interval is (7.8, 9.6). selected and the alcohol content of each bottle is determined. Let u denote the average alcohol content for the population of all bottles of the brand under study. Suppose that the (a) Would a 90% confidence interval calculated from this same sample have been narrower or wider than the given interval? Explain your reasoning. O The 90% would be narrower since the z critical value for 90% is smaller than the z critical value for 95%. O The 90% would be the same since the z critical value for 90% is the same as the z critical value for 95%. O The 90% would be wider since the z critical value for 90% is larger than the z critical value for 95%. O The 90% would be wider since the z critical value for 90% is smaller than the z critical value for 95%. O The 90% would be narrower since the z critical value for 90% is larger than the z critical value for 95%. (b) Consider the following statement: There is a 95% chance that u is between 7.8 and 9.6. Is this statement correct? Why or why not? O It is not a correct statement. We are 95% confident in the general procedure for creating the interval, but the mean may or may not be enclosed in this interval. O It is not a correct statement. There is a 5% chance that the mean is between these values. O It is not a correct statement. Each interval contains the mean by definition. O It is a correct statement. Each interval contains the mean by definition. O It is a correct statement. There is only a 5% chance that the mean is not between these values. (c) Consider the following statement: We can be highly confident that 95% of all bottles of this type of cough syrup have an alcohol content that is between 7.8 and 9.6. Is this statement correct? Why or why not? O It is not a correct statement. The interval is an estimate for the sample mean, not a boundary for sample values. O It is a correct statement. This is the definition of a confidence interval. O It is not a correct statement. The interval is an estimate for the population mean, not a boundary for population values. O It is a correct statement. This interval is a great estimate of boundaries for population values. O t is not a correct statement. The interval is an estimate for the sample mean, not a boundary for population values. (d) Consider the following statement: If the process of selecting a sample of size 50 and then computing the corresponding 95% interval is repeated 100 times, s95 of the resulting intervals will include u. Is this statement correct? Why or why not? O It is not a correct statement. We expect 95 out of 100 intervals will contain the mean, but we don't know this to be true. O t is a correct statement. This is guaranteed by the definition of confidence interval.
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