ErinWeeks 3 years ago Help would be appreciated (: Find the values of the 30th and 90th percentiles of the data. 129, 113, 200, 100, 105, 132, 100, 176, 146, 152 A. 30th percentile = 105; 90th percentile = 200 B. 30th percentile = 113; 90th percentile = 200 C. 30th percentile = 105; 90th percentile = 176 D. 30th percentile = 113; 90th percentile = 176

1. ErinWeeks

@jim_thompson5910 .. do you know this ?

2. jim_thompson5910

First sort the values 129, 113, 200, 100, 105, 132, 100, 176, 146, 152 becomes 100, 100, 105, 113, 129, 132, 146, 152, 176, 200

3. jim_thompson5910

The 30th percentile is the point where 30% of the data is below that value

4. ErinWeeks

but them in order . okay ! i did that part . & what does that mean ?

5. jim_thompson5910

So if you have say 100 values, then 30% of that (0.3*100 = 30 values) are below the 30th percentile

6. ErinWeeks

so in this case we have 10 right .

7. jim_thompson5910

yes, I'm looking up a percentile formula now, one sec

8. ErinWeeks

okay !

9. jim_thompson5910

hmm there are multiple percentile formulas, so it depends on what your book says...do you have your book with you?

10. ErinWeeks

yes let me look quick !

11. ErinWeeks

my book doesnt have a formula .. it just says percentiles : seperate data sets into 100 equal parts

12. jim_thompson5910

well i found one formula to be n = (P/100)*N + 1/2 So the 30th percentile is at... n = (30/100)*10 + 1/2 n = 300/100 + 1/2 n = 3 + 1/2 n = 3.5 which rounds to n = 4, so the 4th value (which is 113) is the 30th percentile

13. jim_thompson5910

If we use the same formula for the 90th percentile, then... n = (P/100)*N + 1/2 So the 30th percentile is at... n = (90/100)*10 + 1/2 n = 900/100 + 1/2 n = 9 + 1/2 n = 9.5 which rounds to 10 so the 10th value, which is 200, is the 90th percentile

14. jim_thompson5910

so if we're using the correct formula (I hope we are), then the answer is B. 30th percentile = 113; 90th percentile = 200

15. ErinWeeks

okay i get that ! (: thank you so much

16. jim_thompson5910

let me know if it's the right answer or not

17. mushinni

yup, you were right :)

18. jim_thompson5910

thanks for the confirmation

19. mushinni

thanks for explaining :)