Question

The population standard deviation for the heights of dogs in inches in a city is 3.9 inches. If we want to be 90% confident that the sample mean is within 2 inches of the true population mean. What is the minimum sample size that can be taken?

Z0.10

1.282

Z0.05

1.645

Z0.025

1.960

Z.0.01

2.326

Z0.005

2.576

Answer #1

Solution :

Given that,

Population standard deviation = = 3.9

Margin of error = E = 2

At 90% confidence level the z is ,

= 1 - 90% = 1 - 0.90 = 0.10

/ 2 = 0.10 / 2 = 0.05

Z_{/2}
= Z_{0.05} = 1.645

sample size = n = (Z_{/2}*
/ E) ^{2}

n = (1.645 * 3.9/ 2)^{2}

n = 10.2897

n = 11

**Sample size = 11**

he population standard deviation for the heights of dogs, in
inches, in a city is 6.5 inches. If we want to be 95% confident
that the sample mean is within 2 inches of the true population
mean, what is the minimum sample size that can be taken? z0.10
z0.05 z0.04 z0.025 z0.01 z0.005 1.282 1.645 1.751 1.960 2.326 2.576
Use the table above for the z-score, and be sure to round up to the
nearest integer.

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inches, in a city is 7.8 inches. If we want to be 95% confident
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mean, what is the minimum sample size that can be taken?
z0.10
z0.05
z0.04
z0.025
z0.01
z0.005
1.282
1.645
1.751
1.960
2.326
2.576
Use the table above for the z-score, and be sure to round up to
the nearest integer.
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z0.05
z0.04
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estimated (sample) proportion is within 5 percentage points of the
true population proportion of customers who are males? z0.10 z0.05
z0.04 z0.025 z0.01 z0.005 1.282 1.645 1.751 1.960 2.326 2.576 Use
the table of values above?

Suppose the manager of a shoe store wants to determine the
current percentage of customers who are males. How many customers
should the manager survey in order to be 92% confident that the
estimated (sample) proportion is within 5 percentage points of the
true population proportion of customers who are males?
z0.10
z0.05
z0.04
z0.025
z0.01
z0.005
1.282
1.645
1.751
1.960
2.326
2.576
Use the table of values above.

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current percentage of customers who are males. How many customers
should the manager survey in order to be 99% confident that the
estimated (sample) proportion is within 5 percentage points of the
true population proportion of customers who are males?
z0.10
z0.05
z0.04
z0.025
z0.01
z0.005
1.282
1.645
1.751
1.960
2.326
2.576
Use the table of values above.

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z0.05
z0.04
z0.025
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