Standard Deviation


I receive this error code: Oops, try again. grades_std_deviation(2.1875) returned 1.0399139475 instead of the expected: 1.4790199458

I am just not sure why my standard deviation calculation is not working correctly. Any suggestions?

grades = [100, 100, 90, 40, 80, 100, 85, 70, 90, 65, 90, 85, 50.5]

def print_grades(grades):
    for grade in grades:
        print grade

def grades_sum(grades):
    total = 0
    for grade in grades: 
        total += grade
    return total
def grades_average(grades):
    sum_of_grades = grades_sum(grades)
    average = sum_of_grades / float(len(grades))
    return average

def grades_variance(scores):
    for score in scores:
    return variance/len(scores)
print grades_variance(grades)
def grades_std_deviation(variance):
    return squared
print grades_std_deviation(variance)


** means 'to the power of'. So the line squared = variance ** .05 calculates variance to the power of 0.05 and stores the result to the variable squared. Moving the decimal place ** 0.5 would give you the square root (variance to the power of 0.5).


Thank you! Silly mistake to make on my part; I appreciate your help!


You're welcome!

You may also want to rename squared to square_root to reflect what the function grades_std_deviation is doing.


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