tolerance (version 0.4.0)

anovatol.int: Tolerance Intervals for ANOVA

Description

Tolerance intervals for each factor level in a balanced (or nearly-balanced) ANOVA.

Usage

anovatol.int(lm.out, data, alpha = 0.05, P = 0.99, side = 1,
             method = c("HE", "WBE", "EXACT"), m = 50)

Arguments

lm.out

An object of class lm (i.e., the results from the linear model fitting routine such that the anova function can act upon).

data

A data frame consisting of the data fitted in lm.out. Note that data must have one column for each main effect (i.e., factor) that is analyzed in lm.out and that these columns must be of class factor

alpha

The level chosen such that 1-alpha is the confidence level.

P

The proportion of the population to be covered by this tolerance interval.

side

Whether a 1-sided or 2-sided tolerance interval is required (determined by side = 1 or side = 2, respectively).

method

The method for calculating the k-factors. The k-factor for the 1-sided tolerance intervals is performed exactly and thus the same for either method chosen. "HE" is the Howe method and is often viewed as being extremely accurate, even

m

The maximum number of subintervals to be used in the integrate function. This is necessary only for method = "EXACT". The larger the number, the more accurate the solution. Too low of a value can result in an error.

Value

• anovatol.int returns a list where each element is a data frame corresponding to each main effect (i.e., factor) tested in the ANOVA and the rows of each data frame are the levels of that factor. The columns of each data frame report the following:
• mean
  The mean for that factor level.
• n
  The effective sample size for that factor level.
• k
  The k-factor for constructing the respective factor level's tolerance interval.
• 1-sided.lower
  The 1-sided lower tolerance bound. This is given only if side = 1.
• 1-sided.upper
  The 1-sided upper tolerance bound. This is given only if side = 1.
• 2-sided.lower
  The 2-sided lower tolerance bound. This is given only if side = 2.
• 2-sided.upper
  The 2-sided upper tolerance bound. This is given only if side = 2.

References

Howe, W. G. (1969), Two-Sided Tolerance Limits for Normal Populations - Some Improvements, Journal of the American Statistical Association, 64, 610--620. Weissberg, A. and Beatty, G. (1969), Tables of Tolerance Limit Factors for Normal Distributions, Technometrics, 2, 483--500.

See Also

K.factor, normtol.int, lm, anova

Examples

## 90\%/95\% 2-sided tolerance intervals for a 2-way ANOVA 
## using the "warpbreaks" data.

attach(warpbreaks)

lm.out <- lm(breaks ~ wool + tension)
out <- anovatol.int(lm.out, data = warpbreaks, alpha = 0.10,
                    P = 0.95, side = 2, method = "HE")
out

plottol(out, x = warpbreaks)