N | Systematic | Random | Clustered | |
---|---|---|---|---|

Estimated population variance | 10 | 1.019 | 1.026 | 0.584 |

20 | 1.003 | 1.013 | 0.757 | |

50 | 1.011 | 1.033 | 0.904 | |

100 | 1.007 | 0.997 | 0.969 | |

Standard deviation of estimates | 10 | 0.477 | 0.478 | 0.810 |

20 | 0.288 | 0.330 | 0.616 | |

50 | 0.151 | 0.192 | 0.401 | |

100 | 0.024 | 0.131 | 0.284 | |

Proportion of autocorrelated pairs | 10 | 0.00 | 0.016 | 0.448 |

20 | 0.00 | 0.016 | 0.218 | |

50 | 0.00 | 0.016 | 0.089 | |

100 | 0.00 | 0.016 | 0.048 |

The autocorrelated data were generated by dividing an ordered vector of 500 random values from a standard normal distribution into groups of five consecutive values. The entire groups and the values within each group were reordered at random, representing a hypothetical transect where always five neighboring locations would show very similar values, with random steps between groups. The data set has an expected variance of 1.0 and the proportion of (autocorrelated) within-group comparisons is 0.016. Three types of samples were taken from the transect: (i) a random sample from all locations, (ii) a systematic sample selecting every fifth location, and (iii) a clustered sample, where entire groups of five neighboring locations were selected at random. Data simulation and sampling were repeated 1000 times for each sample size of 10, 20, 50, or 100.