```{r, setup, include=FALSE}
require(mosaic)
```

## The number of breaks in yarn during weaving

The following dataset contains the results of an experiment where the number of yarn breaks during weaving are measured for two different types of wool at three different levels of string tension.

```{r}
data(warpbreaks)
head(warpbreaks)
```

Perform a one way analysis of variance (ANOVA) of the `warpbreaks` data with `breaks` as response and `tension` as factor/explanatory variable. Remember to first plot the data. Then make a model in `R` using `lm`. Write down the prediction equation. Use the prediction equation to calculate the predicted mean number of breaks for each tension level. Is the mean number of breaks the same for all tensions?

Next, perform a two way analysis of variance with both wool type and tension as factors and no interaction. Remember to make plot(s). Write down the prediction equation. Use the prediction equation to calculate the predicted mean number of breaks for each combination of wool and tension. Investigate if there is an interaction between wool and tension.