Anyone able to give me any assistance with the following piece of code? I am just trying to create a stats table for the differences in scores in an exam but I keep getting the following error:

Error in summarise(min = min(diffs), max = max(diffs), mean = mean(diffs), :

object 'diffs' not found

My code is:

```
exam.data = read.csv(file="Exam.csv")
exam.data = exam.data %>%
mutate(diffs=Final-Exam2)
ggplot(data=exam.data, aes(y=diffs)) + geom_boxplot()
summarise(min = min(diffs), max = max(diffs),
mean=mean(diffs),
median=median(diffs),
sd = sd(diffs),
q1 = quantile(diffs, probs = 0.25),
q3 = quantile(diffs, probs = 0.75))
```

I don't get why it gives this error as the boxplot is generated ok. Any help or if someone could point me in the right direction would be greatly appreciated.