Answer:
94
Step-by-step explanation:
Margin of error = E = $ 120
Confidence Level = 95%
The z-score for 95% confidence level from the z-table = z = 1.96
Population standard deviation = σ = $593
Sample size = n = ?
The formula to calculate the margin of error is:
[tex]E=\frac{z \sigma}{\sqrt{n} }[/tex]
Re-arranging the equation, we get:
[tex]\sqrt{n}=\frac{z \sigma}{E}\\\\ n = (\frac{z \sigma}{E})^{2}[/tex]
Using the given values in above equation, we get:
[tex]n=(\frac{1.96 \times 593}{120} )^{2}\\\\ n = 93.8[/tex]
Rounding of to next higher integer, we get n = 94
Thus, we need a sample size of 94 to estimate an unknown population mean μ
