Question 1180195: Suppose that a brand of lightbulb lasts on average 2243 hours with a standard deviation of 199 hours. Assume the life of the lightbulb is normally distributed. Calculate the probability that a particular bulb will last from 1797 to 2406 hours?
P(1797 < X < 2406) =
Enter your answer as a number accurate to 4 decimal places.
*Note: all z-scores must be rounded to the nearest hundredth.
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! z=(x-mean)/sd
z lower=(1797-2243)/199=-2.24
z upper=163/199=0.82
the probability is 0.7813
-
check on calculator with 2 VARS 2 normalcdf (1797,2406,2243,199)ENTER=0.7811, which is slightly more accurate, since the z-values are not rounded until the calculation. This is obtained with 3 decimal places for z.
|
|
|
