Description Usage Arguments Details Value Author(s) References Examples

Function computes sample size for the two-sided Wilcoxon test when applied to two independent samples with ordered categorical responses.

1 | ```
n.wilcox.ord(power = 0.8, alpha = 0.05, t, p, q)
``` |

`power` |
required Power |

`alpha` |
required two-sided Type-I-error level |

`t` |
sample size fraction n/N, where n is sample size of group B and N is the total sample size |

`p` |
vector of expected proportions of the categories in group A, should sum to 1 |

`q` |
vector of expected proportions of the categories in group B, should be of equal length as p and should sum to 1 |

This function approximates the total sample size, N, needed for the two-sided Wilcoxon test when comparing two independent samples, A and B, when data are ordered categorical according to Equation 12 in Zhao et al.(2008). Assuming that the response consists of D ordered categories *C_1 ,..., C_D*. The expected proportions of these categories in two treatments A and B must be specified as numeric vectors *p_1,...,p_D* and *q_1,...,q_D*, respectively. The argument t allows to compute power for an unbalanced design, where *t=n_B/N* is the proportion of sample size in treatment B.

`total sample size` |
Total sample size |

`m` |
Sample size group 1 |

`n` |
Sample size group 2 |

Ralph Scherer

Zhao YD, Rahardja D, Qu Yongming. Sample size calculation for the Wilcoxon-Mann-Whitney test adjsuting for ties. Statistics in Medicine 2008; 27:462-468

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