Question

2 Packets of crisps from a production line have a weight distribution that is normal with a mean of 50.0 grams and a standard deviation of 2.0 grams. Samples are taken of size 36.

1. What is the probability that a sample mean is less than 49.0 grams? (Give answer to four decimal places.)

2. What would be the control limits for a three standard error control chart in these circumstances? Give your answer in the format (to the nearest gram):

3. What proportion of sample means would be outside the these control limits? (Give your answer as a percentage, accurate to 0.1%, leaving out the % sign when you give the answer).

only need help with part 3

Answer 1

Normal distribution: 99.7% is approximately +/- 3 standard deviations around the mean. 0.3% is outside those limits.