Maximum error in confidence interval

Question

A sample of $40$ cows is drawn to estimate the mean weight of a large herd of cattle. If the standard deviation of the sample is $96$ kg, what is the maximum error in a $90\text{%}$ confidence interval estimate?

Answer 1

You use t-distribution since you have sample standard deviation $s = 96$, and with $n = 40,\alpha = 0.1,df = 39, t_{\frac{\alpha}{2}}$ = ? ( can you look it up the table A-3 in Triola book ? ) . Thus $ E = t_{\frac{\alpha}{2}}\cdot \dfrac{s}{\sqrt{n}} $ is your formula.