Roll And Keep

Comparing roll and keep with +N capped at 4

It looks like roll and keep is roughly 1/2 as effective as a +N capped at 4, except you don't have to do math. So

• 5dF is like +1
• 7dF is like +2
• 9dF is like +3.

Cumulative probabilities for rolling extra dF dice and keeping the best 4:

	+0dF	+1dF	+2dF	+3dF	+4dF	+5dF
4	1.23	4.53	10.01	17.33	25.86	34.97
3	6.17	16.87	29.22	41.34	52.32	61.86
2	18.52	37.45	54.6	67.9	77.5	84.23
1	38.27	60.08	75.99	86.15	92.14	95.52
0	61.73	79.01	89.3	94.83	97.61	98.93
-1	81.48	91.36	96.16	98.35	99.31	99.72
-2	93.83	97.53	99.04	99.63	99.86	99.95
-3	98.77	99.59	99.86	99.95	99.98	99.99
-4	100	100	100	100	100	100

Cumulative probabilities for +N, capping the result at a maximum of 4:

	+0	+1	+2	+3
4	1.23	6.17	18.52	38.27
3	6.17	18.52	38.27	61.73
2	18.52	38.27	61.73	81.48
1	38.27	61.73	81.48	93.83
0	61.73	81.48	93.83	98.77
-1	81.48	93.83	98.77	100
-2	93.83	98.77	100
-3	98.77	100
-4	100