A quality analyst wants to construct a sample mean chart for controlling a packaging process. He knows from past experience that whenever this process is in control, package weight is normally distributed with a mean of $20$ ounces and a standard deviation of two ounces. Each day last week, he randomly selected four packages and weighed each:

Day Weight $($ounces$)$

Monday $23222324$

Tuesday $23211921$

Wednesday $20192021$

Thursday $18192019$

Friday $18202220$

What is the standard deviation of the sampling distribution of sample means for whenever this process is in control?

Multiple Choice

$0\mathrm{.}4$ ounces

$0\mathrm{.}1$ ounces

$2$ ounces

$1$ ounce

$0\mathrm{.}5$ ounces