Question

Bags of pretzels are sampled to ensure proper weight. The overall average for the samples is 10 ounces. Each sample contains 30 bags. The standard deviation is estimated to be 4 ounces. With a 99.7% confidence interval, develop a control chart with upper and lower control limits. Briefly discuss your findings.

Please show work!!

Answer 1

Following are the given details :

Sample size = n = 30 bags

Overall average = m = 10 ounce

Standard deviation of sample = Sd = 4 Ounce

The Z values for 99.7% confidence level = NORMSINV ( 0.9985) = 2.9677

Therefore,

Upper Control Limit = m + z x sd/ square root ( n ) = 10 + 2.9677 x 4/ Square root( 30) = 10 + 11.8708/5.477 = 10 + 2.167 = 12.167 ounce

Lower Control Limit = m – z x sd / Square root ( n ) = 10 – 2.9677 x 4 /Square root ( 30) = 10 – 11.8708/5.477 = 10 – 2.167 = 7.833 ounce