# Math

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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

• Math -

The standard deviation, σ, is \$50. The mean is \$900.
To spend less than \$750 means that the spending is less than mean - 3σ.
The probability of this happening, assuming the spending follows the normal distribution curve, can be found from the normal distribution tables, for example:
http://www.math.unb.ca/~knight/utility/NormTble.htm
where the probability for the tail end of 3σ is 0.001350, or 0.135%.

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