tooth {bootstrap} | R Documentation |

## Tooth Strength Data

### Description

Thirteen accident victims have had the strength of their teeth measured,
It is desired to predict teeth strength from measurements not requiring
destructive testing. Four such bvariables have been obtained for
each subject, (`D1`

,`D2`

) are difficult to obtain,
(`E1`

,`E2`

) are easy to obtain.

### Usage

`data(tooth)`

### Format

A data frame with 13 observations on the following 6 variables.

- patient
a numeric vector

- D1
a numeric vector

- D2
a numeric vector

- E1
a numeric vector

- E2
a numeric vector

- strength
a numeric vector

### Details

Do the easy to obtain variables give as good prediction as the difficult
to obtain ones?

### Source

Efron, B. and Tibshirani, R. (1993) An Introduction to the Bootstrap.
Chapman and Hall, New York, London.

### Examples

```
str(tooth)
mod.easy <- lm(strength ~ E1+E2, data=tooth)
mod.diffi <- lm(strength ~ D1+D2, data=tooth)
summary(mod.easy)
summary(mod.diffi)
if(interactive())par(ask=TRUE)
theta <- function(ind) {
easy <- lm(strength ~ E1+E2, data=tooth, subset=ind)
diffi<- lm(strength ~ D1+D2, data=tooth, subset=ind)
(sum(resid(easy)^2) - sum(resid(diffi)^2))/13 }
tooth.boot <- bootstrap(1:13, 2000, theta)
hist(tooth.boot$thetastar)
abline(v=0, col="red2")
qqnorm(tooth.boot$thetastar)
qqline(tooth.boot$thetastar, col="red2")
```

[Package

*bootstrap* version 2019.6

Index]