Question

A publisher wants to estimate the mean length of time (in minutes) all adults spend reading newspapers. To determine this estimate, the publisher takes a random sample of 15 people and obtains the results below. From past studies, the publisher assumes sigma is 2.1 minutes and that the population of times is normally distributed.

6 10 12 6 6 10 7 7 8 8 11 11 9 10 7

Construct the 90% and 99% confidence intervals for the population mean. Which interval is wider? If convenient, use technology to construct the confidence intervals.

The 90% confidence interval is ( ____, ____ ). (Round to one decimal place as needed.)

Answer #1

First we need to find the sample mean is:

Following is the screen shot of excel for 90% confidence interval:

Following is the output generated by excel:

Confidence interval - mean | ||

90% | confidence level | |

8.53 | mean | |

2.1 | std. dev. | |

15 | n | |

1.645 | z | |

0.892 | half-width | |

9.422 | upper confidence limit | |

7.638 | lower confidence limit |

The 90% confidence interval is (7.6, 9.4).

---------------------

Following is the output generated by excel for 99% confidence interval:

Confidence interval - mean | ||

99% | confidence level | |

8.53 | mean | |

2.1 | std. dev. | |

15 | n | |

2.576 | z | |

1.397 | half-width | |

9.927 | upper confidence limit | |

7.133 | lower confidence limit |

The 99% confidence interval is (7.1, 9.9).

A publisher wants to estimate the mean length of time (in
minutes) all adults spend reading newspapers. To determine this
estimate, the publisher takes a random sample of 15 people and
obtains the results below. From past studies, the publisher
assumes sigma σ is 2.1 minutes and that the population of times is
normally distributed. 6 9 6 11 6 7 10 12 8 6 8 9 10 10 9
Construct the 90% and 99% confidence intervals for the
population...

A publisher wants to estimate the mean length of time (in
minutes) all adults spend reading newspapers. To determine this
estimate, the publisher takes a random sample of 15 people and
obtains the results below. From past studies, the publisher
assumes sigma is 1.9 minutes and that the population of times is
normally distributed. 10 10 8 10 10 6 10 11 7 9 7 7 8 12 11
Construct the 90% and 99% confidence intervals for the population
mean....

A publisher wants to estimate the mean length of time (in
minutes) all adults spend reading newspapers. To determine this
estimate, the publisher takes a random sample of 15 people and
obtains the results below. From past studies, the publisher
assumes sigma is 2.7 minutes and that the population of times is
normally distributed. 12 12 6 9 11 12 9 9 11 10 6 6 12 6 6
Construct the 90% and 99% confidence intervals for the population
mean....

A publisher wants to estimate the mean length of time? (in
minutes) all adults spend reading newspapers. To determine this?
estimate, the publisher takes a random sample of 15 people and
obtains the results below. From past? studies, the publisher
assumes standard deviation is 1.7 minutes and that the population
of times is normally distributed.
9
10
6
8
11
7
10
8
7
12
12
11
9
9
9
Construct the? 90% and? 99% confidence intervals for the
population...

publisher wants to estimate the mean length of time (in
minutes) all adults spend reading newspapers. To determine this
estimate, the publisher takes a random sample of 15 people and
obtains the results below. From past studies, the publisher
assumes sigmaσ is1.9 minutes and that the population of times is
normally distributed.
11
7
8
12
7
11
6
6
9
9
7
8
10
8
10
Construct the 90% and 99% confidence intervals for the
population mean. Which interval...

A publisher wants to estimate the mean length of time (in
minutes) all adults spend reading newspapers. To determine this
estimate, the publisher takes a random sample of 15 people and
obtains the results below. From past studies, the publisher
assumes
sigmaσ
is
2.22.2
minutes and that the population of times is normally
distributed.
99
88
99
1111
66
99
99
77
1212
77
1212
66
99
1212
99
Construct the 90% and 99% confidence intervals for the
population mean....

A research council wants to estimate the mean length of time (in
minutes) that the average U.S. adult spends watching television
using digital video recorders (DVR’s) each day. To determine the
estimate, the research council takes random samples of 35 U.S.
adults and obtains the following times in minutes.
24
27
26
29
33
21
18
24
23
34
17
15
19
23
25
29
36
19
18
22
16
45
32
12
24
35
14
40
30
19
14...

A research council wants to estimate the mean length of time (in
minutes) that the average U.S. adult spends watching television
using digital video recorders (DVR’s) each day. To determine the
estimate, the research council takes random samples of 35 U.S.
adults and obtains the following times in minutes.
24
27
26
29
33
21
18
24
23
34
17
15
19
23
25
29
36
19
18
22
16
45
32
12
24
35
14
40
30
19
14...

You are given the sample mean and the sample standard deviation.
Use this information to construct the? 90% and? 95% confidence
intervals for the population mean. Which interval is? wider? If?
convenient, use technology to construct the confidence intervals. A
random sample of 39 gas grills has a mean price of ?$643.60 and a
standard deviation of ?$56.60 The? 90% confidence interval is __ ,
___

You want to estimate the mean time
college students spend watching online videos each day. The
estimate must be within 2 minutes of the population mean. Determine
the required sample size to construct a 99% confidence interval for
the population mean. Assume that the population standard deviation
is 4.4 minutes. Leave as an integer.

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