The quality-control manager at a light bulb factory has determined the mean life of a light bulb ...

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The quality-control manager at a light bulb factory has determined the mean life of a light bulb is 755 hours with a std dev of 80 hrs
a)what percentage of light bulbs last between 770 and 790 hrs
b) how long would a light bulb have to last to be in the 98th percentile for longevity
c) what is the probability that a sample of 400 light bulbs would have a sample mean above 760?
d)What is the probability that a sample of 1600 light bulbs would have a sample mean above 760?

    • 8 years ago
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    μ = 755, σ = 80 (a) z = (x - μ)/σ ...
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