Question

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.

Answer 1

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