Question

If the population standard deviation σ=25. What is the required minimum sample size to construct a 95 confidence level for the population mean with an allowable error of ±3?

Answer 1

The required minimum sample size to construct a 95% confidence level for the population mean is 267.

In this question,

In the probability and statistics theory, the confidence interval of the population parameter is the estimated range of values we are sure with a certainty that our parameter will lie within, the range being calculated from the sample obtained. The smaller is the margin of error, the more confidence we have in our results.

The population standard deviation, σ = 25

Confidence level for the population mean = 95%

Margin of error = ±3

Let n be the sample size of the population

The z-score for the confidence level of 95% for the population mean is 1.96.

The formula of margin of error is

$E=\frac{z \sigma}{\sqrt{n} }$

Now, the sample size of the population can be calculated as

$n=(\frac{z\sigma}{E} )^{2}$

On substituting the above values,

⇒ $n=(\frac{(1.96)(25)}{3} )^{2}$

⇒ $n=(\frac{49}{3}) ^{2}$

⇒ $n=(16.33)^{2}$

⇒ n = 266.77 ≈ 267

Hence we can conclude that the required minimum sample size to construct a 95% confidence level for the population mean is 267.

Learn more about sample size of the population here

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