Laboratory tests show that the lives of light bulbs are normally distributed with a mean of 750 hours and a standard deviation of 75 hours. Find the probability that randomly selected light bulb will last between 825 and 900 hours.
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Answer:
0.135
Step-by-step explanation:
Laboratory tests show that the lives of light bulbs are normally distributed with a mean of 750 hours and a standard deviation of 75 hours. Find the probability that randomly selected light bulb will last between 825 and 900 hours.
Z = (Data point - Mean)/Standard deviation
Mean = 725
Standard deviation = 75
Data points = 825 & 900
Z for 825 hrs = ( 825 - 750)/75 = 1
Z for 900 hrs = ( 900 - 750)/75 = 2
Between 825 and 900 = Z score 2 - Z score 1
Z score between 1 & 2 ( 1 sided ) = (1/2)( 0.95 - 0.68)
= 0.27/2
= 0.135
Probability that selected light bulb will last between 825 and 900 hours.
= 0.135/1
= 135/1000
= 27/200
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