In one D&D campaign I played years ago, we had to roll our stats with the usual "roll 4D6 and drop lowest" rule, however with a special exception, that is, **if all four dice had the same result, you got to keep them all**.

So for example rolling 5, 5, 5, 5 would net you a 20 while a 5, 5, 5, 6 would be a 16.

What is the average advantage this rolling scheme would have given us?

## Best Answer

The advantage in general is pretty low since the chance of that happening is small. The chance of rolling 4 identical numbers on d6s is \$\frac{6}{6^4} = \frac{1}{216} \approx 0.46\%\$. That would make the expected value of the roll rise by \$\frac{3.5}{216}\approx0.016\$ attribute points.

The more important effect is that there is an actual possibility of starting with a 24 in an attribute (or more with a racial bonus). Also there is no chance of starting with a 3. Whether this is something you want is up to you.