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It is known that the population variance equals 484. With a 0.95 probability, calculate the sample size that needs to be taken to estimate the population mean if the desired margin of error is 5 or less?
What is Pbar and how do we determine it's value?
Is the variance information we don't need?

Respuesta :

Answer:

The sample size is 74

Pbar = 0.05

The variance information is needed

Step-by-step explanation:

The population variance , [tex]\sigma^{2} = 484[/tex]

[tex]\sigma = 22[/tex]

Confidence Interval level = 95% = 0.95

Significance Interval = 1 - CI

Significance Interval = 1 - 0.95 = 0.05

Error margin = 5

The critical value = [tex]Z_{\frac{\alpha}{2} } = Z_{0.025}[/tex] = 1.96 (From the z table)

The sample size is given by:

[tex]n \geq (\frac{Z_{\alpha /2} * \sigma}{E} )^{2}[/tex]

[tex]n \geq (\frac{1.96 * 22}{5}) ^{2}[/tex]

[tex]n \geq 74.373\\n \geq 75[/tex]

[tex]\bar{P} = 1 - P[/tex]

Since P = 0.95

[tex]\bar{P} = 1 - 0.95\\\bar{P} = 0.05[/tex]

The variance information is needed in this question when calculating the sample size