A Company That Manufactures Health Food Snacks Produces Low Sodium

A company that manufactures health food snacks produces low sodium rice chips. To monitor the process for sodium levels, chips are selected periodically and the amount of sodium (mg) measured. For each of thirty samples consisting of 8 chips, the mean and range in sodium content is determined. The average of the means across all samples is 55 mg and the average range is 2.2 mg. The estimated process standard deviation ( ) is

A) 0.773 mg.
B) 2.683 mg.
C) 0.073 mg.
D) 16.176 mg.
E) 1.833 mg.