How to calculate standard deviation of concrete Standard deviation of concrete is the root mean square deviation of all results. Standard deviation is generally denoted by s OR σ. Mathematical formula to calculate standard deviation is as per following
Sample calculation of standard deviation of concrete cube results
| No of tests | Test Result x | Average | Deviation | Square of deviation |
| 1 | 44 | 40.05 | 3.95 | 15.60 |
| 2 | 40 | -0.05 | 0.00 | |
| 3 | 39 | -1.05 | 1.10 | |
| 4 | 42 | 1.95 | 3.80 | |
| 5 | 38 | -2.05 | 4.20 | |
| 6 | 35 | -5.05 | 25.50 | |
| 7 | 45 | 4.95 | 24.50 | |
| 8 | 41 | 0.95 | 0.90 | |
| 9 | 36 | -4.05 | 16.40 | |
| 10 | 38 | -2.05 | 4.20 | |
| 11 | 42 | 1.95 | 3.80 | |
| 12 | 40 | -0.05 | 0.00 | |
| 13 | 39 | -1.05 | 1.10 | |
| 14 | 44 | 3.95 | 15.60 | |
| 15 | 38 | -2.05 | 4.20 | |
| 16 | 44 | 3.95 | 15.60 | |
| 17 | 42 | 1.95 | 3.80 | |
| 18 | 36 | -4.05 | 16.40 | |
| 19 | 40 | -0.05 | 0.00 | |
| 20 | 38 | -2.05 | 4.20 | |
| Total | 801 | 160.95 |
Standard Deviation = SqRoot ( 160.95 / (20-1)) = 2.91