I really need help with this problem I cannot figure it out.
A survey was conducted to measure the number of hours per day that adults in the US spend on computers. In the survey, the number of hours were normally distributed, with a mean of 7 hours and a standard deviation of 1 hour. If 45 adults in the US are randomly selected, how many would you expect to say they spend more than 5.75 hours a week on the computer?
the answer that I got is 4.752
I was just wondering if this is correct because the only other problem in the book says less than not more than.
Thanks.
A survey was conducted to measure the number of hours per day that adults in the US spend on computers. In the survey, the number of hours were normally distributed, with a mean of 7 hours and a standard deviation of 1 hour. If 45 adults in the US are randomly selected, how many would you expect to say they spend more than 5.75 hours a week on the computer?
the answer that I got is 4.752
I was just wondering if this is correct because the only other problem in the book says less than not more than.
Thanks.
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normalize the number
(5.75 - 7) / 1 = -1.25
go to the z chart and find where z=-1.25
p=0.1056
that is p for z<-1.25 but you want z>-1.25 so just take 1-p
p = 1-0.1056 = 0.8944
there are 45 adults so the number of adults would be
45(p) = 45(0.8944) = 40.25 adults
(5.75 - 7) / 1 = -1.25
go to the z chart and find where z=-1.25
p=0.1056
that is p for z<-1.25 but you want z>-1.25 so just take 1-p
p = 1-0.1056 = 0.8944
there are 45 adults so the number of adults would be
45(p) = 45(0.8944) = 40.25 adults