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The lifetime of lightbulbs that are advertised to last for 3900 hours are normally distributed with...

The lifetime of lightbulbs that are advertised to last for 3900 hours are normally distributed with a mean of 4100 hours and a standard deviation of 300 hours. What is the probability that a bulb lasts longer than the advertised figure?

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Expert Solution

Given that the distribution is normal with mean=4100 and a standard deviation of 300 hence the probability will be calculated using the Z score and Z table shown below.

Thus Z score at X=3900 is calculated as:

Hence the probability that it last more than advertised is P(X>3900) =P(Z>0.67) which is computed using Z table shown below as:

P(Z>0.67)=1-0.7486

=0.2564

milcah answered 5 months ago
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