rats {BayesDA} | R Documentation |

## Tumor Incidence in Historical Control Groups and Current Group of Rats

### Description

In the evaluation of drugs for possible clinical application, studies
are routinely performed on rodents. For a particular study drawn from the
statistical literature, suppose the immediate aim is to estimate theta,
the probability of tumor in a population of female laboratory rats of type
'F344' that receive a zero dose of the drug — a control group. This
gives data from historical control groups, and one current experimental control group.

### Usage

`data(rats)`

### Format

A data frame with 71 observations on the following 3 variables.

`y`

number of rats with tumors

`N`

number of rats in experiment

`Current`

a factor with levels `0`

`1`

### Examples

```
data(rats)
summary(rats)
# moment estimate of (alfa, beta) in beta distribution is (1.4, 8.6)
with(subset(rats, Current=="0"), hist( y/N, freq=FALSE))
plot(function(x) dbeta(x, 1.4, 8.6), from=0, to=1, col="red", add=TRUE)
# plotting posterior in same plot:
plot(function(x) dbeta(x, 5.4, 18.6), from=0, to=1, col="blue", add=TRUE)
```

[Package

*BayesDA* version 2012.04-1

Index]