Answer:
The warranty period should be of 32 months.
Step-by-step explanation:
Normal Probability Distribution
Problems of normal distributions can be solved using the z-score formula.
In a set with mean and standard deviation
, the z-score of a measure X is given by:
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.
Mean time before failure of 40 months with a standard deviation of 6 months.
This means that
What should be the warranty period, in months, so that the manufacturer will not have more than 10% of the blenders returned?
The warranty period should be the 10th percentile, which is X when Z has a p-value of 0.1, so X when Z = -1.28.
The warranty period should be of 32 months.
