confintr (version 1.0.0)

ci_var: CI for the Population Variance

Description

This function calculates CIs for the population variance. By default, classic CIs are calculated based on the chi-squared distribution, assuming normal distribution (see Smithson). Bootstrap CIs are also available (default: "bca"). We recommend them for the non-normal case.

Usage

ci_var(
  x,
  probs = c(0.025, 0.975),
  type = c("chi-squared", "bootstrap"),
  boot_type = c("bca", "perc", "stud", "norm", "basic"),
  R = 9999L,
  seed = NULL,
  ...
)

Value

An object of class "cint" containing these components:

• parameter: Parameter specification.

• interval: CI for the parameter.

• estimate: Parameter estimate.

• probs: Lower and upper probabilities.

• type: Type of interval.

• info: Additional description.

Arguments

x

A numeric vector.

probs

Lower and upper probabilities, by default c(0.025, 0.975).

type

Type of CI. One of "chi-squared" (default) or "bootstrap".

boot_type

Type of bootstrap CI ("bca", "perc", "stud", "norm", "basic"). Only used for type = "bootstrap".

R

The number of bootstrap resamples. Only used for type = "bootstrap".

seed

An integer random seed. Only used for type = "bootstrap".

...

Further arguments passed to boot::boot().

Details

The stud (bootstrap t) bootstrap uses the standard error of the sample variance given in Wilks.

References

1. Smithson, M. (2003). Confidence intervals. Series: Quantitative Applications in the Social Sciences. New York, NY: Sage Publications.

2. S.S. Wilks (1962), Mathematical Statistics, Wiley & Sons.

See Also

ci_sd.

Examples

x <- 1:100
ci_var(x)
ci_var(x, type = "bootstrap", R = 999)  # Use larger R