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A random sample of size [tex]n=604[/tex] from a population whose parameter is [tex]p=0.33[/tex].

a. What is the mean of the distribution of sample proportions? Round the answer to 2 decimal places.
[tex]\mu_{\bar{p}} = \square[/tex]

b. What is the standard deviation of the distribution of sample proportions? Round the answer to 2 decimal places.
[tex]\sigma_{\bar{p}} = \square[/tex]

Sagot :

To find the mean and standard deviation of the distribution of sample proportions for a random sample of size [tex]\( n = 604 \)[/tex] from a population with a population proportion [tex]\( p = 0.33 \)[/tex], we can proceed as follows:

### Part (a)
Mean of the Distribution of Sample Proportions

The mean ([tex]\(\mu_{\bar{p}}\)[/tex]) of the distribution of sample proportions is equal to the population proportion [tex]\( p \)[/tex].

So,
[tex]\[ \mu_{\bar{p}} = p = 0.33 \][/tex]

Therefore,
[tex]\[ \mu_{\bar{p}} = 0.33 \][/tex]

### Part (b)
Standard Deviation of the Distribution of Sample Proportions

The standard deviation ([tex]\(\sigma_{\bar{p}}\)[/tex]) of the distribution of sample proportions is calculated using the formula:
[tex]\[ \sigma_{\bar{p}} = \sqrt{\frac{p(1 - p)}{n}} \][/tex]

First, we substitute the given values into the formula:
[tex]\[ \sigma_{\bar{p}} = \sqrt{\frac{0.33 \cdot (1 - 0.33)}{604}} \][/tex]

Simplifying the expression inside the square root first,
[tex]\[ 0.33 \cdot (1 - 0.33) = 0.33 \cdot 0.67 = 0.2211 \][/tex]

Then divide by the sample size [tex]\( n \)[/tex]:
[tex]\[ \frac{0.2211}{604} \approx 0.000366 \][/tex]

Taking the square root of the result:
[tex]\[ \sigma_{\bar{p}} = \sqrt{0.000366} \approx 0.0191 \][/tex]

Rounding to 2 decimal places,
[tex]\[ \sigma_{\bar{p}} \approx 0.02 \][/tex]

Therefore,
[tex]\[ \sigma_{\bar{p}} = 0.02 \][/tex]

### Summary

a. The mean of the distribution of sample proportions ([tex]\(\mu_{\bar{p}}\)[/tex]) is:
[tex]\[ \mu_{\bar{p}} = 0.33 \][/tex]

b. The standard deviation of the distribution of sample proportions ([tex]\(\sigma_{\bar{p}}\)[/tex]) is:
[tex]\[ \sigma_{\bar{p}} = 0.02 \][/tex]