Question

1. In a sample of 64 Pasadena residents the mean age was 57.8 years. From the census it's known that the age has a standard deviation of 6.5 years. Find a 90% confidence interval for the population mean age. (Note: CL=0.90)

2.

The following table list the number of white mathematicians mentioned in a sample of 30 textbooks.

4 |
6 |
6 |
7 |
9 |
9 |
10 |
10 |
11 |

13 |
13 |
14 |
15 |
17 |
17 |
18 |
18 |
19 |

19 |
21 |
21 |
22 |
22 |
22 |
22 |
22 |
17 |

15 |
8 |
20 |

If it is known that the standard deviation is 5 mathematicians, find a 99% confidence interval for the population mean.

Answer #1

We would be looking at the first question here on confidence interval.

Q1) We are given the population standard deviation here, therfore we will use standard normal tables, to get the critical value here.

For 90% confidence level, we have from standard normal
tables:

P(-1.645 < Z < 1.645) = 0.9

therefore the confidence interval for the population mean here is computed as:

**This is the required 90% confidence interval for the
population mean here.**

Assuming that the population standard deviation is
unknown, calculate the 95% confidence interval of the
population mean.
The following is the data. Calculating Process should be shown
by Excel (Formulas). What formulas in statistics are used?
7
21
23
24
18
16
2
19
11
6
3
13
17
9
5
12
13
17
4
14
15
25
12
24
22
14
14
20
15
11
26
17
21
11
4
13
16
14
13
14
25
23
9
15...

Male and female populations of humpback whales under 80 years
old are represented by age in the table below. Complete parts (a)
through (d).
Age Males Females
0-9 (10) (6)
10-19 (17) (9)
20-29 (13) (15)
30-39 (16) (19)
40-49 (24) (24)
50-59 (21) (25)
60-69 (19) (19)
70-79 (12) (13)
Find the population mean and the standard deviation of age for
males and Females

The following sample was taken from a normally distributed
population:
3, 4, 5, 5, 6, 6, 6, 7, 7, 9, 10, 11, 12, 12, 13, 13, 13, 14,
15
(a) Compute the 0.95 confidence interval on the population
mean
(b) Compute the 0.90 confidence interval on the population
standard deviation

2.
Based on a sample data of 64 children mean age of children in the
summer camp A is 12,4 years with Standard deviation 3 years.
Estimate the average age of children in whole population.
Population size is 8100
a) Find the point estimation for average age
b) With 95% confidence, what is the margin of error? With 90%
confidence, what is the margin of error?
c) What is the 95% confidence interval estimate of the population
mean (mean children...

In a survey of randomly selected subjects, the mean age of 40
respondents is 36.4 years, and the sample standard deviation of all
ages is known to be 10.1 years. Construct a 95% confidence interval
estimate of the mean age of the population from which the sample
was selected.

____________________________________________
The results of a sample of 372 subscribers to Wired
magazine shows the time spent using the Internet during the week.
Previous surveys have revealed that the population standard
deviation is 10.95 hours. The sample data can be found in the Excel
test data file.
What is the probability that another sample of 372 subscribers
spends less than 19.00 hours per week using the Internet?
____________________________________________
Develop a 95% confidence interval for the population mean
____________________________________________
If the editors...

A random sample of 16 pharmacy customers showed the waiting
times below (in minutes).
20, 27, 24, 23, 19, 21, 18, 17
22, 15, 18, 32, 16, 20, 19, 19
Find a 90 percent confidence interval for μ, assuming that the
sample is from a normal population. (Round your standard deviation
answer to 4 decimal places and t-value to 3 decimal places. Round
your answers to 3 decimal places.) The 90% confidence interval
_____ to _____

Consider the following data from a random sample: 23 12 26 14 20
25 14 11 21 14 25 21 22 21 8 19 17 22 17 16
a.) Construct a stem-and-leaf plot and specify the five-number
index (min, Q1, Q2, Q3, & max)
b.) Compute the mean and the standard deviation
c.) Find a 95% confidence interval for the population mean.

A random sample of 144 observations has a mean of 20, a median
of 21, and a mode of 22. The population standard deviation is known
to equal 3.6. The 90% confidence interval for the population mean
is
19.62 to 20.38
19.51 to 20.49
19.41 to 20.59
19.30 to 20.70

Let the following sample of 8 observations be drawn from a
normal population with unknown mean and standard deviation: 28, 23,
18, 15, 16, 5, 21, 13. [You may find it useful to reference
the t table.]
a. Calculate the sample mean and the sample
standard deviation. (Round intermediate calculations to at
least 4 decimal places. Round "Sample mean" to 3 decimal places and
"Sample standard deviation" to 2 decimal places.)
b. Construct the 90% confidence interval for
the population...

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