wBoot (version 1.0.3)

boot.cond.mean.per: Percentile Bootstrap Conditional Mean CI in Simple Linear Regression

Description

Determines a confidence interval for a conditional mean in simple linear regression, using the percentile bootstrap method.

Usage

boot.cond.mean.per(x, y, xp, conf.level = 0.95, R = 9999)

Arguments

x

a (nonempty) numeric vector of predictor-variable data values.

y

the corresponding numeric vector of response-variable data values.

xp

the value of the predictor variable for which to find the CI for the conditional mean of the response variable.

conf.level

the confidence level (between 0 and 1); default is 0.95.

R

the number of bootstrap replications; default is 9999.

Value

• A list with class "boot.regcor" containing the following components:
• Boot.values
  the point estimates (fits) obtained from the bootstrap.
• Confidence.limits
  the upper and lower limits of the confidence interval.
• Header
  the main title for the output.
• Variable.1
  the predictor variable.
• Variable.2
  the response variable.
• n
  the sample size.
• Statistic
  the name of the statistic, here fit.
• Observed
  the observed point estimate (fit).
• Replications
  the number of bootstrap replications.
• Mean
  the mean of the bootstrap values.
• SE
  the standard deviation of the bootstrap values.
• Bias
  the difference between the mean of the bootstrap values and the observed value.
• Percent.bias
  the percentage bias: 100*|Bias/Observed|.
• Null
  always NULL for this function.
• Alternative
  always NULL for this function.
• P.value
  always NULL for this function.
• p.value
  always NULL for this function.
• Level
  the confidence level.
• Type
  always NULL for this function.
• Confidence.interval
  the confidence interval.
• cor.ana
  a logical; always FALSE for this function.

Warning

This routine should be used only when bias is small and the sampling distribution is roughly symmetric, as indicated by the output of the bootstrap. Otherwise, use the BCa version.

concept

• Bootstrap
• Percentile bootstrap
• Simple linear regression
• Confidence interval
• Conditional mean in simple linear regression

Examples

# Lot size, house size, and value for a sample of homes in a particular area.
data("homes")
str(homes)
attach(homes)

# 95% (default) CI for the conditional mean value of a 3000 sq.ft. home,
# with 999 bootstrap replications.
boot.cond.mean.per(HOUSE.SIZE, VALUE, 3000, R = 999)

# 90% CI for the conditional mean value of a 3000 sq.ft. home, with
# 999 bootstrap replications.
boot.cond.mean.per(HOUSE.SIZE, VALUE, 3000, conf.level = 0.90, R = 999)

detach(homes) # clean up