SOLUTION: The duration of phone calls to a Calling Centre is normally distributed with a mean of seven minutes and a standard deviation of two minutes. Calculate the probability that a p

Question 914107: The duration of phone calls to a Calling Centre is normally distributed with a mean of
seven minutes and a standard deviation of two minutes. Calculate the probability that a
phone call to the Calling Centre last for between 5 to 10 minutes.
(b) A recent survey found that 56% of mobile phone users, between the ages of 18 to 34,
had a smartphone. Suppose a random sample of 100 mobile phone users were selected.
What is the probability that less than 50 of them have a smartphone?
Answer by ewatrrr(24785) (Show Source): You can put this solution on YOUR website!
mean = 7, sd = 2
P( 5 < x < 10) = normalcdf(-100, 3/2) - normalcdf(-100, -1) = .9332 - .1587 = .7745 0r 77.45%
0r may Use
P( 5 < x < 10) = normalcdf(-1, 3/2)
P( 5 < x < 10) Area between the green lines (z = -1 and z = 1.5)

..........

b) P( x < .50) = normacdf(-100, -1.2087) = .1134 0r 11.34%
= -1.2087
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