A teacher grading statistics homeworks finds that none of the students has made more than three errors.14% have made three errors,25% have made two errors,and 39% have made one error.Find the standard deviation of the number of errors in students' statistics homeworks.
A)0.97
B)0.93
C)0.89
D)1.07
E)0.82

Question

Quizplus · Accepted Answer

The standard deviation is the square root of the variance. The variance is the average of the squared deviations from the mean. The mean is the average of the data. The deviations from the mean are the differences between the data and the mean. The squared deviations from the mean are the squares of the deviations from the mean. The average of the squared deviations from the mean is the variance. The square root of the variance is the standard deviation.The mean is (0*0.14) + (1*0.39) + (2*0.25) + (3*0.14) = 1.21.The variance is (0-1.21)^2*0.14 + (1-1.21)^2*0.39 + (2-1.21)^2*0.25 + (3-1.21)^2*0.14 = 0.93.The standard deviation is the square root of 0.93, which is 0.96.

A Teacher Grading Statistics Homeworks Finds That None of the Students