I have the following data:

```
dat <- data.frame(ID=1:4,q1=c(2,3,2,3),q2=c(3,2,2,4),q3=c(2,2,3,5),q4=c(4,4,4,6))
ID  q1 q2 q3 q4 
1    2  3  2  4
2    3  2  2  4 
3    2  2  3  4
4    3  4  5  6

```

I need to have :

1. the mean of q1 and q3; the mean q2 and q4
2. the mean of q1 and q2; the mean of q3 and q4

E.g. - for the first one: 2+2/2= 2 (q1+q3) ...etc for each row