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What sample size is needed to give the desired margin of error in estimating a population mean with the indicated level of confidence? A margin of error within ±12 with \(95 \%\) confidence, assuming we estimate that \(\sigma \approx 125\)

Short Answer

Expert verified
The required sample size to estimate the population mean with a margin of error ±12 and a level of confidence of 95% is 107.

Step by step solution

01

Identify known values

First, we confirm the values provided in the problem. From the problem, it’s known that the margin of error \(E=12\), the standard deviation \(\sigma = 125\), and the value of z for a 95% confidence level is approximately 1.96 (using a Z-table or similar resource).
02

Apply the formula for the margin of error

The formula to calculate the margin of error when the population standard deviation is known can be expressed as \(E = Z * \frac{σ}{\sqrt{n}}\). We can rearrange this formula to isolate \(n\), getting \(\sqrt{n} = \frac{Z * σ}{E}\) or \(n = (\frac{Z * σ}{E})^2\). Plug in the known values: \(n = (\frac{1.96 * 125}{12})^2\).
03

Calculate Sample Size

Perform the calculation inside the parenthesis first then square the result. It gets approximately 106.72. Since we cannot have a fraction of a participant, we should always round up to ensure the sample size is sufficiently large. Therefore, the smallest necessary sample size is 107.

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