Grace is looking at a report of her monthly cell-phone usage for the last year to determine if she needs to upgrade her plan. the list represents the approximate number of megabytes of data grace used each month.

700, 735, 680, 890, 755, 740, 670, 785, 805, 1050, 820, 750

what is the standard deviation of the data? round to the nearest whole number.

65

75

100

130

In order to find the standard deviation, we first have to calculate the mean (average) of the numbers. To get this we add all the numbers together and then divide by 12 since there are 12 numbers. The mean = 782. Next, we take each number and subtract the mean, taking the result and squaring it. For this we get: 6724, 2209, 10404, 11664, 729, 1764, 12544, 9, 529, 71824, 1444, 1024. Now we sum all of these up and take the average by dividing the sum by 12. Doing this we get 120868/12=10072. The last step is the take the square root of that number to get the standard deviation. The final result is 100.