Mean | Use enough decimal places to give either the SD to two significant digits,7 or the SE to one significant digit | 3320 g |

3.32 kg |

Percentage | Integers, or one decimal place for values under 10%. Values over 90% may need one decimal place if their complement is informative. Use two or more decimal places only if the range of values is less than 0.1% | 0.1% |

5.3% |

27% |

89% |

99.6% |

Mean difference | Use enough decimal places to give the SE to one or two significant digits. For a standardised mean difference use one or two decimal places | |

Regression coefficient | As with the mean difference. | |

Correlation coefficient | One or two decimal places, or more when very close to ±1 | 0.03 |

−0.7 |

0.89 |

0.999 |

Risk ratio | Round to two significant digits if the leading non-zero digit is four or more, otherwise round to three (the rule of four11). Alternatively use one/two significant digits rather than two/three. For ORs very close to 1 (eg, in logistic regression with a continuous variable) use three decimal places or else report the log OR×100 as the percentage odds to one decimal place13 | 0.0321 |

0.062 |

0.76 |

1.05 |

4.2 |

11.3 |

55 |

1.042 |

4.1% |

SD | One or two significant digits7 | 570 g |

0.57 kg |

9 mm Hg |

2.5 mL |

SE | One or two significant digits | |

CI | Use the same rule as for the corresponding effect size (be it mean, percentage, mean difference, regression coefficient, correlation coefficient or risk ratio), perhaps with one less significant digit | |

Test statistics: t, F, χ^{2}, etc | Up to one decimal place and up to two significant digits | |

t=−1.3 |

F=11 |

χ^{s}=4.1 |

p value | Round up to one significant digit, within the limits shown in the examples. The lower limit may be smaller than 0.001, but never 0.000. For genome-wide association studies use the power of 10 format | >0.9 |

0.4 |

0.1 |

0.08 |

0.05 |

0.003 |

<0.001 |

6.10^{−9} |