Nest function

Calculate the N required to estimate the ICC with a desired confidence interval

Given a predicted ICC and k measures per individual/group, this function will calculate the N individuals/groups required to obtain a desired confidence interval w(Bonett 2002).

Nest(
  est.type = c("hypothetical", "pilot"),
  w,
  ICC = NULL,
  k = NULL,
  x = NULL,
  y = NULL,
  data = NULL,
  alpha = 0.05
)

Arguments

• est.type: A character string of either "hypothetical" indicating usage of the given values of k and ICC or if "pilot"

  is specified then to calculate these from the dataset provided. Just the first letter may be used.

• w: A numeric of desired width for the confidence interval about the ICC estimate.

• ICC: The expected intraclass correlation coefficient.

• k: The number of measurements per individual or group.

• x: A column name of data indicating the individual or group ID from a pilot study.

• y: A column name of data indicating the measurements from a pilot study.

• data: A data.frame from a pilot experiment.

• alpha: The alpha level to use when estimating the confidence interval.

Returns

data.frame indicating the N number of individuals or groups to use to estimate the given ICC with a desired confidence interval width. Rows represent different levels of ICC while columns indicate different levels of k measurements per individual/group.

Details

More than one ICC or k may be given. In this case, the return value is a dataframe with rows representing the values of the specified ICCs and the columns yield the different k values.

Examples

# Example 1
  n1<-Nest("h", w = 0.14, ICC = 0.1, k = 10)
  n1
# Example 2
  data(ChickWeight)
  Nest("p", w = 0.14, x = Chick, y = weight, data = ChickWeight)
  ex2 <- ICCest(Chick, weight, ChickWeight)
  ex2$UpperCI - ex2$LowerCI #confidence interval width of pilot study
  ex2
# Example 3
  Nest("h", w = 0.14, ICC = seq(0.05, 0.15, 0.05), k = seq(10, 12, 1))

References

D.G. Bonett. 2002. Statistics in Medicine, 21(9): 1331-1335.

M.E. Wolak, D.J. Fairbairn, Y.R. Paulsen. 2011. Methods in Ecology and Evolution, 3(1):129-137.

See Also

effort

Author(s)

matthewwolak@gmail.com