The mean lifetime of a tire is 36 months with a variance of 49.
If 126 tires are sampled, what is the probability that the mean of the sample would be less than 36.44 months? Round your answer to four decimal places.
Solution :
Given that,
mean = = 36
2 = 49
standard deviation = = 7
n = 126
= 36
= / n = 7 / 126=0.62
P( <36.44 ) = P[( - ) / < (36.44-36) /0.62 ]
= P(z < 0.71)
Using z table
= 0.7611
probability=0.7611
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