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Vsevolod [243]
3 years ago
13

A simple random sample of items resulted in a sample mean of . The population standard deviation is . a. Compute the confidence

interval for the population mean. Round your answers to one decimal place. ( , ) b. Assume that the same sample mean was obtained from a sample of items. Provide a confidence interval for the population mean. Round your answers to two decimal places. ( , ) c. What is the effect of a larger sample size on the interval estimate? Larger sample provides a - Select your answer - margin of error.
Mathematics
1 answer:
Varvara68 [4.7K]3 years ago
4 0

Answer:

(a): The 95% confidence interval is (46.4, 53.6)

(b): The 95% confidence interval is (47.9, 52.1)

(c): Larger sample gives a smaller margin of error.

Step-by-step explanation:

Given

n = 30 -- sample size

\bar x = 50 -- sample mean

\sigma = 10 --- sample standard deviation

Solving (a): The confidence interval of the population mean

Calculate the standard error

\sigma_x = \frac{\sigma}{\sqrt n}

\sigma_x = \frac{10}{\sqrt {30}}

\sigma_x = \frac{10}{5.478}

\sigma_x = 1.825

The 95% confidence interval for the z value is:

z = 1.960

Calculate margin of error (E)

E = z * \sigma_x

E = 1.960 * 1.825

E = 3.577

The confidence bound is:

Lower = \bar x - E

Lower = 50 - 3.577

Lower = 46.423

Lower = 46.4 --- approximated

Upper = \bar x + E

Upper = 50 + 3.577

Upper = 53.577

Upper = 53.6 --- approximated

<em>So, the 95% confidence interval is (46.4, 53.6)</em>

Solving (b): The confidence interval of the population mean if mean = 90

First, calculate the standard error of the mean

\sigma_x = \frac{\sigma}{\sqrt n}

\sigma_x = \frac{10}{\sqrt {90}}

\sigma_x = \frac{10}{9.49}

\sigma_x = 1.054

The 95% confidence interval for the z value is:

z = 1.960

Calculate margin of error (E)

E = z * \sigma_x

E = 1.960 * 1.054

E = 2.06584

The confidence bound is:

Lower = \bar x - E

Lower = 50 - 2.06584

Lower = 47.93416

Lower = 47.9 --- approximated

Upper = \bar x + E

Upper = 50 + 2.06584

Upper = 52.06584

Upper = 52.1 --- approximated

<em>So, the 95% confidence interval is (47.9, 52.1)</em>

Solving (c): Effect of larger sample size on margin of error

In (a), we have:

n = 30     E = 3.577

In (b), we have:

n = 90    E = 2.06584

<em>Notice that the margin of error decreases when the sample size increases.</em>

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