Ex: The mean shelf life of a spice is 13.4 weeks and the standard deviation is 1.8 weeks.
(a) Would a shelf life of 20 weeks be unusual? Why?
(b) Find the z-score for a shelf life of 15.5 weeks.
(c) What percentage of shelf lives would be expected to be between 13.4 and 15.5 weeks?
Step 1 :Given: mean (
Step 2 :Calculate the z-score for a shelf life of 20 weeks:
Step 3 :
Step 4 :A shelf life of 20 weeks is unusual because its z-score (3.67) is outside the typical range of z-scores (-2 to 2)
Step 5 :Calculate the z-score for a shelf life of 15.5 weeks:
Step 6 :
Step 7 :Using a standard normal distribution table or calculator, find the area between z-scores of 0 and 1.17, which is approximately 38.2%
Step 8 :