```r
cor.test(data = frequency[frequency$author == "Brontë Sisters",],
         ~ proportion + `Jane Austen`)
```

```
## 
## 	Pearson's product-moment correlation
## 
## data:  proportion and Jane Austen
## t = 119.64, df = 10404, p-value < 2.2e-16
## alternative hypothesis: true correlation is not equal to 0
## 95 percent confidence interval:
##  0.7527837 0.7689611
## sample estimates:
##       cor 
## 0.7609907
```

```r
cor.test(data = frequency[frequency$author == "H.G. Wells",], 
         ~ proportion + `Jane Austen`)
```

```
## 
## 	Pearson's product-moment correlation
## 
## data:  proportion and Jane Austen
## t = 36.441, df = 6053, p-value < 2.2e-16
## alternative hypothesis: true correlation is not equal to 0
## 95 percent confidence interval:
##  0.4032820 0.4446006
## sample estimates:
##      cor 
## 0.424162
```