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anonymous

  • one year ago

A random number generator picks a number from 1 to 9 in a uniform manner. Find the 90th percentile. (Round your answer to one decimal place.) My set up is (k-9)(1/8)=0.90 why is this wrong

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  1. nincompoop
    • one year ago
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    why did you use that "set up?"

  2. anonymous
    • one year ago
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    in my book it says to use it

  3. anonymous
    • one year ago
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    (base)(height)=0.90

  4. nincompoop
    • one year ago
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    first, what do you know about percentile rank in your own words

  5. anonymous
    • one year ago
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    isn't it like how many # were chosen...90%?

  6. nincompoop
    • one year ago
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    so you're being asked for the number that ranks 90th percentile

  7. anonymous
    • one year ago
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    right

  8. nincompoop
    • one year ago
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    how would you look for that number

  9. anonymous
    • one year ago
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    that's where I am getting confused because my set up is wrong? would it be like 90%..of 9

  10. nincompoop
    • one year ago
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    let us list your numbers

  11. nincompoop
    • one year ago
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    is this how you have it set up? 1, 2, 3, 4, 5, 6, 7, 8, 9

  12. anonymous
    • one year ago
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    okay yes

  13. nincompoop
    • one year ago
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    there are two ways to get percentile ranks one is: \(\sf \huge \frac{B\times (0.5E)}{n} \times 100 \) B: scores below x E: number of scores equal x n: total number the other is: \(\sf \huge \frac{B}{n} \times 100 \)

  14. nincompoop
    • one year ago
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    if you're going to use the second one, the set up should be \(\sf \large \frac{B}{9} \times 100 = 90 \) remember that your B will be lower than the actual score you're looking for, but let us focus on properly solving for B first

  15. anonymous
    • one year ago
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    so it would be 8.1?

  16. anonymous
    • one year ago
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    8?

  17. anonymous
    • one year ago
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    I thought it ment to keep the .1

  18. nincompoop
    • one year ago
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    http://www.wolframalpha.com/input/?i=%28100*b%29%2F9+%3D+90

  19. nincompoop
    • one year ago
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    round off is the same as estimation and you need to learn about place values.

  20. nincompoop
    • one year ago
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    9.1 rounded off to 1 decimal means you focus on the first decimal if it is between 0-4 then it becomes 0 if it is between 5-9 then you add 1 to the number that preceded it 9.1 = 9 9.5 = 10 9.67 = 10 etcetera etcetera

  21. nincompoop
    • one year ago
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    let us check if our answer makes sense http://www.wolframalpha.com/input/?i=8%2F9

  22. anonymous
    • one year ago
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    I understand that, but the question says "Round your answer to one decimal place" so therefore the answer would be like "9.4" keeping the 4

  23. nincompoop
    • one year ago
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    8 out 9 makes almost 90%

  24. nincompoop
    • one year ago
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    no

  25. anonymous
    • one year ago
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    when I practice another problem with numbers 2-9 and asking for the 80th percentile, the answer is 7.6 ??

  26. anonymous
    • one year ago
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    the .6 is kept

  27. nincompoop
    • one year ago
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    http://www.mathsisfun.com/rounding-numbers.html

  28. nincompoop
    • one year ago
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    you're right you keep it

  29. anonymous
    • one year ago
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    so youre saying when it is smaller than .4 it is rounded to 0

  30. nincompoop
    • one year ago
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    but 1, 2, 3, 4, 5, 6, 7, 8, 9 tell me where is 8.1

  31. anonymous
    • one year ago
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    so you're saying the answer is 8

  32. nincompoop
    • one year ago
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    in scores 1 - 9 and if they are just 1, 2 .... 9 then yes unless someone actually has a score of 8.1 then it is 8.1

  33. anonymous
    • one year ago
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    so I tried 8.1 and 8 and it is saying it is wrong

  34. nincompoop
    • one year ago
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    how about the first formula

  35. anonymous
    • one year ago
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    the one that I used? nope

  36. nincompoop
    • one year ago
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    I made a typo \(\huge \frac{(B + 0.5E )}{n} \times 100 \)

  37. nincompoop
    • one year ago
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    so 8.1 and 8.0 are wrong huh?

  38. anonymous
    • one year ago
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    yes

  39. nincompoop
    • one year ago
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    did you put 8.0 with point?

  40. anonymous
    • one year ago
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    no I just did 8

  41. nincompoop
    • one year ago
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    try 8.0 because of the 10th place value

  42. nincompoop
    • one year ago
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    did it work?

  43. anonymous
    • one year ago
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    wait but I only have one try left so I would like to be really sure!

  44. anonymous
    • one year ago
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    the book says 8.2??

  45. nincompoop
    • one year ago
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    I don't know what you just did in the end, kropot but I do want to know why 8.2 because I want to learn if there's any other methods of solving this.

  46. anonymous
    • one year ago
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    I am really not sure. They give me an example of "random number generator picks a number from 2 to 9 in a uniform manner. Find the 80th percentile(Round your answer to one decimal place . and the answer is 7.6 I am trying to work backwards from the answer but I still do not know

  47. dan815
    • one year ago
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    (7.6-2)/(9-2)=0.8

  48. dan815
    • one year ago
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    using same method, (k-1)/(9-1)=0.9 k=?

  49. dan815
    • one year ago
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    k=8.2

  50. anonymous
    • one year ago
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    ohohoh I see

  51. anonymous
    • one year ago
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    thank you so much for this explanation!!!!

  52. anonymous
    • one year ago
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    what was the equation you used tho?

  53. dan815
    • one year ago
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    i looked at the example they gave you

  54. dan815
    • one year ago
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    basically what they are doing is

  55. dan815
    • one year ago
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    |dw:1436852959460:dw|

  56. dan815
    • one year ago
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    and they gave you this example |dw:1436853055768:dw|

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