### Abstract

Yuen's two-sample trimmed mean test statistic is one of the most robust methods to apply when variances are heterogeneous. The present study develops formulas for the sample size required for the test. The formulas are applicable for the cases of unequal variances, non-normality and unequal sample sizes. Given the specified a and the power (I - β), the minimum sample size needed by the proposed formulas under various conditions is less than is given by the conventional formulas. Moreover, given a specified size of sample calculated by the proposed formulas, simulation results show that Yuen's test can achieve statistical power which is generally superior to that of the approximate t test. A numerical example is provided.

Original language | English |
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Pages (from-to) | 137-146 |

Number of pages | 10 |

Journal | British Journal of Mathematical and Statistical Psychology |

Volume | 60 |

Issue number | 1 |

DOIs | |

Publication status | Published - 2007 May 1 |

### All Science Journal Classification (ASJC) codes

- Statistics and Probability
- Arts and Humanities (miscellaneous)
- Psychology(all)