Description Usage Arguments Value Note Author(s) References See Also Examples

A function to calculate the appropriate sample size *per group* for the (unstandardized) ANOVA contrast
so that the width of the confidence interval is sufficiently narrow.

1 2 |

`error.variance` |
the common error variance; i.e., the mean square error |

`c.weights` |
the contrast weights |

`width` |
the desired full width of the obtained confidence interval |

`conf.level` |
the desired confidence interval coverage, (i.e., 1 - Type I error rate) |

`assurance` |
parameter to ensure that the obtained confidence interval width is narrower than the desired width with a specified degree of certainty (must be NULL or between zero and unity) |

`certainty` |
an alias for |

`MSwithin` |
an alias for |

`SD` |
the standard deviation of the common error in ANOVA model |

`...` |
allows one to potentially include parameter values for inner functions |

`n` |
the necessary sample size |

Be sure to use the error varaince and not its square root (i.e., the standard deviation of the errors).

Ken Kelley (University of Notre Dame; [email protected]), Keke Lai

Kelley, K., Maxwell, S. E., & Rausch, J. R. (2003). Obtaining power or obtaining
precesion: Delineating methods of sample size planning. *Evaluation and the Health Professions, 26*, 258–287.

Maxwell, S. E., & Delaney, H. D. (2004). *Designing experiments and analyzing data: A model
comparison perspective*. Mahwah, NJ: Erlbaum.

`ss.aipe.sc`

, `ss.aipe.c.ancova`

, `ci.c`

1 2 3 4 5 6 7 | ```
# Suppose the population error variance of some three-group ANOVA model
# is believed to be 40. The researcher is interested in the difference
# between the mean of group 1 and the average of means of group 2 and 3.
# To plan the sample size so that, with 90 percent certainty, the
# obtained 95 percent full confidence interval width is no wider than 3:
ss.aipe.c(error.variance=40, c.weights=c(1, -0.5, -0.5), width=3, assurance=.90)
``` |

MBESS documentation built on Jan. 11, 2018, 1:08 a.m.

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