Answer:
It should be 100 days sample so that the margin of error will be 39.2 tons or less
Step-by-step explanation:
We are given that A coal company wants to determine a 95% confidence interval estimate for the average daily tonnage of coal that it mines.
[tex]\alpha = 0.05[/tex]
To Find two tailed critical value using Z table
[tex]Z_{\frac{\alpha}{2}}=Z_{\frac{0.05}{2}}=\pm 1.96[/tex]
Margin of error = ME = 39.2
[tex]\sigma = 200[/tex]
Formula : [tex]n = (\frac{Z_{\frac{\alpha}{2}} \times \sigma}{ME})^2[/tex]
[tex]n = (\frac{1.96 \times 200}{39.2})^2[/tex]
n=100
Hence it should be 100 days sample so that the margin of error will be 39.2 tons or less
