posted by Lori .
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
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:
where the probability for the tail end of 3σ is 0.001350, or 0.135%.