The Weight of a Product Is Measured in Pounds $\bar { X }$

Multiple Choice

The weight of a product is measured in pounds.A sample of 50 units is taken from a batch.The sample yielded $\bar { X }$
= 75 lbs. ,and we know that ?² = 100 lbs.Calculate a 90 percent confidence interval for ?.

A) $[ 73.19$$\quad$$\quad$$76.81 ]$
B) $\left[ \begin{array} { l l } 51.74 & 98.26\end{array} \right]$
C) $\left[ \begin{array} { l l } 72.67 & 77.33\end{array} \right]$
D) $\left[ \begin{array} { l l } 67.50 & 82.50\end{array} \right]$