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18. Explaining confidence The admissions director from Big City University found that (107.8, 116.2) is a 95% confidence interval for the mean IQ score of all freshmen. Comment on whether or not each of the following explanations is correct.
(a) There is a 95%probability that the interval from 107.8to 116.2contains .
(b) There is a 95%chance that the interval (107.8,116.2) contains x.
(c) This interval was constructed using a method that produces intervals that capture the true mean in 95% of all possible samples.
(d) 95%of all possible samples will contain the interval (107.8,116.2).

(e) The probability that the interval (107.8,116.2)captures is either 0or 1, but we don鈥檛 know which.

Short Answer

Expert verified

(a) The explanation that there is a 95% probability that the interval from
107.8to 116.2contains is incorrect.

(b) The explanation that there is a 95%chance that the interval (107.8,116.2)contains xis incorrect.

(c) The explanation that the interval was constructed using a method that
produces intervals that capture the true mean in 95%of all possible samples is correct.

(d) The explanation that 95% of all possible samples will contain the inter-
val (107.8,116.2) is incorrect.

(e) The explanation that the probability that the interval (107.8,116.2)captures is either 0or 1is correct.

Step by step solution

01

Part (a) Step 1: Given information

To determine that there is a 95%probability that the interval from 107.8to 116.2 contains is correct or not.

02

Part (a) Step 2: Explanation

Let, the confidence interval is 95%.
And the mean IQis 107.8to116.2.
In the range of 107.8to 116.2, the 95 percent probability does not contain the true population mean of all samples.
As a result, the explanation is incorrect.

03

Part (b) Step 1: Given information

To determine that there is a 95%chance that the interval (107.8,116.2)contains xis correct or not.

04

Part (b) Step 2: Explanation

Let, the confidence interval is 95%.
And the mean IQis 107.8to 116.2.
The probability of finding the sample mean x is 95percent. However, the sample mean x is identical to the confidence interval's center.
Hence, the probability is 1.
As a result, the explanation is incorrect.

05

Part (c) Step 1: Given information

To determine that the interval was constructed using a method that
produces intervals that capture the true mean in 95% of all possible samples is correct or not.

06

Part (c) Step 2: Explanation

Let, the confidence interval is 95%.
And the mean IQis 107.8to 116.2.
The true mean of all possible samples is included within the 95 percent confidence interval between 107.8 and 116.2.
As a result, the explanation is correct.

07

Part (d) Step 1: Given information

To determine that the 95%of all possible samples will contain the interval (107.8,116.2)is correct or not.

08

Part (d) Step 2: Explanation

Let, the confidence interval is 95%.
And the meanIQis 107.8to 116.2.
The interval between 107.8and 116.2does not contain real population mean in the 95 percent probability.
As a result, the samples have a confidence interval of less than 95 percent for all potential samples.
As a result, the explanation is incorrect.

09

Part (e) Step 1: Given information

To determine that the probability that the interval (107.8,116.2)captures is either 0or 1, is correct or not.

10

Part (e) Step 2: Explanation

Let, the confidence interval is 95%.
And the mean IQis 107.8to 116.2.
The confidence interval from 107.8to 116.2 does not contain the true population mean for all samples.

Hence, the probability is either 1or 1.
As a a result, the explanation is correct.

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