Need h‭elp understanding Google Sheets PERCENTIF

Question

I'm just confused here and would like some more insight into what's happening and if it's on my end or not.

I have a Google Sheet with a bunch of quiz data, and I need to calculate the percent error over all respondents. I have the correct answer in column A, the user's input in the respective row in column B, and error in column C as A-B. $\\left\\{ A, B, C \\in \\mathbb{Z} \\right\\}$ <- LaTeX (A, B, and C all contain integers).

Here's my data:

math input	math correctAnswer	math error
93	93	0
84	84	0
110	111	-1
163	163	0
52	52	0
85	85	0
103	103	0
102	112	-10
98	98	0
136	136	0
70	70	0
119	119	0
63	63	0
174	174	0
82	82	0
109	109	0
92	92	0
34	34	0
95	95	0
126	126	0
78	78	0
67	87	-20
164	164	0
116	116	0
100	100	0
19	122	-103
118	118	0
92	91	1
103	103	0
84	84	0
98	98	0
114	114	0
104	114	-10
53	53	0
121	121	0
136	136	0
140	140	0
76	76	0
150	150	0
80	80	0
125	125	0
129	129	0
109	109	0
112	112	0
174	172	2
161	161	0
147	147	0
63	63	0
93	93	0
113	113	0
138	138	0
168	168	0
69	69	0
77	77	0
105	105	0
41	41	0
79	69	10
45	45	0
33	33	0
121	156	-35
116	116	0
169	169	0
111	111	0
137	138	-1
131	131	0
121	121	0
117	117	0
89	89	0
168	168	0
129	129	0
134	134	0
182	182	0
139	139	0
100	100	0
153	153	0
54	54	0
126	126	0
49	49	0
84	84	0
93	93	0
56	56	0
116	116	0
78	78	0
96	96	0
118	118	0
138	138	0
62	62	0
53	53	0
79	79	0
33	33	0
32	32	0
111	111	0
194	194	0
114	124	-10
169	169	0
118	118	0
126	126	0
80	80	0
133	133	0
50	54	-4
156	176	-20
154	164	-10
34	34	0
50	50	0
92	92	0
109	109	0
143	143	0
107	107	0
113	113	0
120	139	-19
84	84	0
92	92	0
41	41	0
77	77	0
59	59	0
108	108	0
115	115	0
122	122	0
128	134	-6
58	58	0
53	53	0
95	95	0
152	152	0
166	166	0
99	99	0
129	129	0
156	156	0
166	166	0
110	110	0
70	70	0
110	149	-39
127	127	0
121	121	0
100	100	0
120	120	0
73	73	0
50	50	0
154	154	0
72	72	0
116	116	0
107	107	0
158	155	3
125	125	0
70	70	0
46	46	0
103	146	-43
153	153	0
46	46	0
118	118	0
112	112	0
108	108	0
118	118	0
76	120	-44
124	124	0
90	90	0
123	123	0
149	149	0
102	102	0
160	160	0
127	127	0
82	82	0
104	104	0
134	134	0

I originally just used COUNTIF(C2:C10000, "=0")/COUNTA(C2:C10000) and made a formula for it, which worked fine, but someone suggested I use PERCENTIF.

They're the same idea, at least documentation-wise, but COUNTIF(C2:C10000, "=0")/COUNTA(C2:C10000) outputs 0.8773006135, which is correct, whereas PERCENTIF(C2:C10000, "=0") outpus 14%, which is neither correct nor the inverse of 0.8773006135.

Is this just really bad floating point precision error? Are these functions actually different?

Answer 1

Blank cells beyond your data range are by default evaluated to zero → so the 14%

either hardcode the range as

=percentif(C2:C164,0)

OR

=percentif(filter(C2:C,C2:C<>""),0)

& you'll see the 87.73%