The NEW electric razor company has just introduced its newest model of electric
ID: 3060299 • Letter: T
Question
The NEW electric razor company has just introduced its newest model of electric razor—So Smooth Shaver. The R&D scientists believe the lives of all shavers follow a normal distribution with mean 48 months and standard deviation 8 months.
A. The company warranties its razors with a money-back guarantee, but wants to limit this warranty to 3% of the razors it sells. For how many months should the company warranty the So Smooth Shaver?
B. If we were to track the lives of a random sample of 16 of these shavers, what is the probability the mean life would exceed 51 months?
Explanation / Answer
a)
for bottom 3 percentile ; z =-1.88
therefore corresponding warranty =mean +z*std deviation = 32.96 monhs
b)
probability the mean life would exceed 51 months:
for normal distribution z score =(X-)/ here mean= = 48 std deviation == 8.0000