Calculate Quartiles From Mean And Standard Deviation. If you think your data are normally distributed the first quartile should be 675 standard deviations below the mean and the third quartile should be 675 above the mean so the interquartile range Q3 minus Q1 should span 135 standard deviations. After that consider first four values Q1 and last four values Q3.
Q3 Q1 2. The Quartile Deviation QD is the product of half of the difference between the upper and lower quartiles. Mean deviation is thus obtained as under.
Or if you have the sample size.
Of Students 20 20 - 25 25- 30 30 - 35 35 - 40 40 - 45 45 - 50 8 1 10 9 6 7 3 2 4 5. Divide the sum of the squared deviations by n 1. To calculate quartile deviation first arrange the given set of data in ascending order find the center value and the find out the n21 value. After that consider first four values Q1 and last four values Q3.
