```r
data<- c(440,340,350,456,470) ## Five observations of reaction time

x<-data-mean(data)  # Subtract the mean from the data
x<-x^2  # Square the results
x<-sum(x)/4  # Divide by n.1 
sqrt(x) # Take the square root
```

```
## [1] 61.45893
```