A quality control expert at LIFE batteries wants to test their new batteries. The design engineer claims they have a standard deviation of 87 minutes with a mean life of 538 minutes. If the claim is true, in a sample of 134 batteries, what is the probability that the mean battery life would be less than 547.9 minutes? Round your answer to four decimal places.
Solution :
Given that,
mean = = 538
standard deviation = = 87
Sample size = n = 134
= 538
= / n = 87 134 =7.5156
P( < 547.9)
P ( - / ) < ( 547.9 - 538 / 7.5156 )
P ( z < 9.9 / 7.5156 )
P ( z < 1.32)
Using z table
= 0.9066
Probability = 0.9066
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