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Consider a large population with \(p=.21\). Assuming \(n / N \leq .05\), find the mean and standard deviation of the sample proportion \(\hat{p}\) for a sample size of a. 400 b. 750

Short Answer

Expert verified
a. For a sample size of 400, the mean is .21 and the standard deviation is computed as \(\sqrt{.21(.79) / 400}\). b. For a sample size of 750, the mean is .21 and the standard deviation is \(\sqrt{.21(.79) / 750}\).

Step by step solution

01

Compute the Mean

First, let's calculate the mean of the sample proportions (\(\mu_{\hat{p}}\)). Since the mean of the sample proportion equals the population proportion, we have \(\mu_{\hat{p}}=p\). Therefore, \(\mu_{\hat{p}}=.21\). There is no need to differentiate between different sample sizes.
02

Compute the Standard Deviation for a Sample Size of 400

Now, we calculate the standard deviation of the sample proportion (\(\sigma_{\hat{p}}\)) for a sample size \(n=400\). We use the formula \(\sigma_{\hat{p}}=\sqrt{p(1-p) / n}\), so the computation would be \(\sigma_{\hat{p}}=\sqrt{.21(.79) / 400}\).
03

Compute the Standard Deviation for a Sample Size of 750

Similarly, for \(n=750\), we calculate \(\sigma_{\hat{p}}\) by plugging \(n=750\) into the formula, i.e., \(\sigma_{\hat{p}}=\sqrt{.21(.79) / 750}\).

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