# 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