Answer:
15.87%
Step-by-step explanation:
Given that:
The mean (μ) = 1000 hours, the standard deviation (σ) = 100 hours.
The z score provides a means of measurement in statistics to determine the variation of a raw score from the mean. The z score is given as:
[tex]z=\frac{x-\mu}{\sigma}[/tex]
To find that a randomly chosen light bulb will last less than 900 hours:
[tex]z=\frac{x-\mu}{\sigma}=\frac{9000-1000}{100}=-1[/tex]
Therefore, P(x < 900) = P(z < -1) = 0.1587 = 15.87%
