Calculating the Standard Deviation from a Frequency Distribution
Number of meals purchased last week on campus by a sample of college students. (This data is fictitious.)
| x value |
f |
f(x) (multiply) |
x2 (square x) |
f (x2) (multiply f*x2) |
| 2 | 1 | 2 | 4 | 4 |
| 3 | 5 | 15 | 9 | 45 |
| 4 | 3 | 12 | 16 | 48 |
| 6 | 1 | 6 | 36 | 36 |
| Sum: | n=10 | Efx = 35 | Efx2 = 133 |
See class notes for formula.
s = 1.08
s2 = 1.17