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Answer:
The probability that a light bulb of that brand lasts between 1175 hr and 1610 hr is 0.8524.
Step-by-step explanation:
Given : Suppose a brand of light bulbs is normally distributed, with a mean life of 1400 hr and a standard deviation of 150 hr.
To find : The probability that a light bulb of that brand lasts between 1175 hr and 1610 hr ?
Solution :
Applying z-score formula,
where, is population mean
is standard deviation
For x=1175 hour,
For x=1610 hour,
The required probability is,
Using z table, the values are
The probability that a light bulb of that brand lasts between 1175 hr and 1610 hr is 0.8524.