Question 204953:
The total amount being spent on personal calls in a month by employees of a company follows a normal distribution with a mean of $900 and a standard deviation of $50 . Find the probability that in a randomly selected month the amount spent on personal calls is less than $750
i cant seem to figure this out or even know where to begin!... i would be so,so,so greatful if someone would point me in the right direction and at least give me some tools!please!
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! The total amount being spent on personal calls in a month by employees of a company follows a normal distribution with a mean of $900 and a standard deviation of $50 . Find the probability that in a randomly selected month the amount spent on personal calls is less than $750
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Draw a normal curve; put u=900 in the middle and sigma = 50 under that.
Mark the 750 point on the horizontal axis(x-axis).
Shade the area under the curve to the left of 750.
That is the area you are looking for.
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Draw a normal curve and let the horizontal axis be "z-scores".
Put 0 in the middle.
Find the z-score of 750:
z(750) = (750-900)/50 = -3
Mark -3 on the z-axis and shade the area to the left of z = -3.
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Now use a calculator, or software, or a z-chart to find the following:
P(x<750) = P(z<-3) = normalcdf(-100,-3) = 0.001350
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I used a TI calculator to find the probability.
Let me know if this "explanation" does not help.
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Cheers,
Stan .
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