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Exam Statistics
Standard Deviation

Great job computing the variance! The last statistic will be much simpler: standard deviation.

The standard deviation is the square root of the variance. You can calculate the square root by raising the number to the one-half power.

### Instructions

1.

Define a function, `grades_std_deviation`, that takes one argument called `variance`.

`return` the result of `variance ** 0.5`

After the function, create a new variable called `variance` and store the result of calling `grades_variance(grades)`.

Finally `print` the result of calling `grades_std_deviation(variance)`.