Description Usage Arguments Details Value References Examples

View source: R/correlation_measures.R

`prec_icc`

returns the sample size or the precision for the given
intraclass correlation.

1 |

`rho` |
desired intraclass correlation. |

`k` |
number of observations per n (subject). |

`n` |
number of subjects. |

`conf.width` |
precision (the full width of the confidence interval). |

`conf.level` |
confidence level. |

Exactly one of the parameters `n`

or `conf.width`

must be passed as NULL,
and that parameter is determined from the others.

Sample size or precision is calculated according to formula 3 in Bonett
(2002), which is an approximation. Whether ICC is calculated for a one-way or
a two-way ANOVA does not matter in the approximation. As suggested by the
author, *5*rho* is added to n, if *k = 2* and *rho ≥ 7*.

n is rounded up to the next whole number using `ceiling`

.

Object of class "presize", a list of arguments (including the computed one) augmented with method and note elements.

Bonett DG (2002). *Sample size requirements for estimating
intraclass correlations with desired precision*. Statistics in Medicine,
21:1331-1335. doi: 10.1002/sim.1108

1 2 3 4 5 6 7 8 9 | ```
# Bonett (2002) gives an example using 4 raters, with an ICC of 0.85 and want
# a confidence width of 0.2. Bonett calculated that a sample size of 19.2 was
# required. This can be done via
prec_icc(0.85, 4, conf.width = 0.2)
# note that \code{presamp} rounds up to the nearist integer.
# Bonett then goes on to estimate the width given the sample size, finding a
# value 'close to 0.2':
prec_icc(0.85, 4, 20)
``` |

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