An electrical company claims that an average life of bulbs it manufacturers is 1200 hours with a standard deviation of 250 hours. If a random sample of 100 bulbs is chosen, what is the probability of the sample mean will be:
a. Greater than 1150 hours?
b. Less than 1250 hours?
c. Betweem 1150 and 1250 hours?
a.
b.
c.P(1150<X<1250)=P(X<1250)-P(X<1150)=0.9772-0.0228=0.9544
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