X	f	Cumulative frequency	%	Cumulative %
12-16	1	1	1/40=2.5	2.5
17-21	2	1+2=3	2/40=5	2.5+5=7.5
22-26	0	3+0=3	0/40=0	7.5+0=7.5
27-31	2	3+2=5	2/40=5	7.5+5=12.5
32-36	5	5+5=10	5/40=12.5	12.5+12.5=25
37-41	8	10+8=18	8/40=20	25+20=45
42-46	7	18+7=25	7/40=17.5	45+17.5=62.5
47-51	6	25+6=31	6/40=15	62.5+15=77.5
52-56	4	31+4=35	4/40=10	77.5+10=87.5
57-61	2	35+2=37	2/40=5	87.5+5=92.5
62-66	1	37+1=38	1/40=2.5	92.5+2.5=95
67-71	2	38+2=40	2/40=5	95+5=100
Total	40		100

1. what is the cumulative frequency for the 22-26 score interval?

2. how many subjects scored in and below the 12-16 score interval?

3. how many subjects scored in and below the 32-36 score interval?

4. what percentage of the subject scored in the 22-26 score interval?

5. what is the approximate percentile rank for a score of 39?

6. what is the approximate percentile rank for a score of 64?

i need explain how we find percentile rank also how in and below the score in details.

Y