The company installs 5000 light bulbs, with each bulb lasting an average of 500 hours. A normal curve was used to approximate the distribution and the standard deviation of 100 hours. The percentage of light bulbs that can be expected to last less than 690 hours is 97.1%.
Given that, mean (μ) = 500 hours and
standard deviation (\sigma) = 100 hours
We want to find, P(X < 690)
P(X < 690) = P(\frac {X -\mu}{\sigma} < \frac {690 -500}{100}) = P(Z < 1.9) = 0.9713
=> P(X < 690) = 0.971
In percentage : 0.971 * 100 = 97.1%
What do you mean by standard deviation?
A standard deviation (or) is a measure of how widely distributed the data is in relation to the mean. A low standard deviation indicates that data is clustered around the mean, whereas a high standard deviation indicates that data is more spread out.
So, the correct answer is 97.1%.
To learn more about Standard Deviation:
https://brainly.com/question/475676
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