In this article:

## Understanding small samples & margin of error

When reviewing subgroup/filtered Idea scores, it’s important to understand the impact reduced data has on our confidence in results.

When *n*=80 for a filtered group, we are only confident that the true interest score for that group is within around +/- 11% of the interest score in the dashboard (the margin of error). Note that the smaller the sample size is, the higher the margin of error is going to be. And at *n*=50, the margin of error is close to +/- 14%.

*See the below table for each sample size and its corresponding margin of error:*

Sample Size | Margin of Error (+/- %) |

200 | 6.93 |

150 | 8.00 |

100 | 9.80 |

80 | 10.96 |

50 | 13.86 |

20 | 21.91 |

This uncertainty will be true for any given question, for example, top 2-box in a monadic grid.

For this reason, we warn you when sample sizes drop below *n*=80, and ideally filtered subgroup analysis is done with a base of at least *n*=200.