Function to solve a probabilty question

You would need to list the combinations of 8 choose 4, calculate the probability of each, then sum.

One way (I had to hide most rows to post):

	A	B	C	D	E	F	G	H	I	J	K
1	A	B	C	D	E	F	G	H	Prob
2	18%	73%	45%	3%	65%	98%	22%	65%	34.63283%		I2: =SUM(I4:I259)
3
4	0	0	0	0	0	0	0	0			A4: =MOD(INT(2*(ROWS($H$4:Me) - 1) / 2 ^ COLUMNS($H$4:Me)), 2)
5	0	0	0	0	0	0	0	1			I4: {=IF(SUM(A4:H4) = 4, PRODUCT(IF(A4:H4 = 0, 1 - $A$2:$H$2, $A$2:$H$2)), "")}
18	0	0	0	0	1	1	1	0
19	0	0	0	0	1	1	1	1	1.07594%
26	0	0	0	1	0	1	1	0
27	0	0	0	1	0	1	1	1	0.01792%
28	0	0	0	1	1	0	0	0
29	0	0	0	1	1	0	0	1
30	0	0	0	1	1	0	1	0
31	0	0	0	1	1	0	1	1	0.00068%
32	0	0	0	1	1	1	0	0
33	0	0	0	1	1	1	0	1	0.11798%
34	0	0	0	1	1	1	1	0	0.01792%
35	0	0	0	1	1	1	1	1
241	1	1	1	0	1	1	0	1
242	1	1	1	0	1	1	1	0
243	1	1	1	0	1	1	1	1
244	1	1	1	1	0	0	0	0	0.00034%
245	1	1	1	1	0	0	0	1
246	1	1	1	1	0	0	1	0
259	1	1	1	1	1	1	1	1

A4: =MOD(INT(2*(ROWS($H$4:Me) - 1) / 2 ^ COLUMNS($H$4:Me)), 2)

Oops:

A4: =MOD(INT(2*(ROWS($H$4:A4) - 1) / 2 ^ COLUMNS($H$4:A4)), 2)