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cnu115

On an exam, a class ended with a mean raw score of 80 with standard deviation of 10. The distribution of grades in the class was approximately normal. If the teacher wants to give "A" to the top 25th percentile (top 25%) of the class, what is the lowest raw score we could get and still get an "A" on the exam?

  • 9 months ago
  • 9 months ago

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  1. dan815
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    |dw:1373527655365:dw|

    • 9 months ago
  2. cnu115
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    standard deviation of 10

    • 9 months ago
  3. dan815
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    lol i mean how many deviation points wud u have to travel, to be left with only 25% area on the right side

    • 9 months ago
  4. dan815
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    look up the probability distribution graph numbers

    • 9 months ago
  5. cnu115
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    Sorry sir, I could not follow you. Could you please explain

    • 9 months ago
  6. dan815
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    look at that and see at what standard deviation you have to be to be left with only 25% area on the right side

    • 9 months ago
  7. dan815
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    |dw:1373530622874:dw|

    • 9 months ago
  8. cnu115
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    Is it 21% with 0.8 standard deviation?

    • 9 months ago
  9. cnu115
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    It is only one standard deviation point above the mean is to be covered. Isn't it? Other please explain

    • 9 months ago
  10. dan815
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    |dw:1373533594767:dw|

    • 9 months ago
  11. dan815
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    how much more deviation does she have to go to cover upto 75%

    • 9 months ago
  12. dan815
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    look at that chart and figure it out

    • 9 months ago
  13. dan815
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    |dw:1373533703309:dw|

    • 9 months ago
  14. dan815
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    its somewhre inbetween 0.5 and 1

    • 9 months ago
  15. dan815
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    id say around 0.75

    • 9 months ago
  16. dan815
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    so 0.75 of 10 = ? 7.5 marks

    • 9 months ago
  17. dan815
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    then 87.5 should be the marks she needs to set it at

    • 9 months ago
  18. dan815
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    im just estimating values here, im sure u got some formulas to calculate the exact z values and stuff

    • 9 months ago
  19. dan815
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    |dw:1373533813410:dw|

    • 9 months ago
  20. cnu115
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    This Z values I am not aware sir. I am just browsing about this

    • 9 months ago
  21. dan815
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    this will give u more accurate vlaue

    • 9 months ago
  22. dan815
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    |dw:1373533861018:dw|

    • 9 months ago
  23. dan815
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    |dw:1373533886859:dw|

    • 9 months ago
  24. dan815
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    |dw:1373533895795:dw|

    • 9 months ago
  25. dan815
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    |dw:1373533946389:dw|

    • 9 months ago
  26. dan815
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    |dw:1373533966949:dw|

    • 9 months ago
  27. dan815
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    |dw:1373533987799:dw|

    • 9 months ago
  28. cnu115
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    |dw:1373534025223:dw|

    • 9 months ago
  29. cnu115
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    what is this equation you have used

    • 9 months ago
  30. dan815
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    5.6/15

    • 9 months ago
  31. dan815
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    because

    • 9 months ago
  32. dan815
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    look at the chart

    • 9 months ago
  33. dan815
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    at 0.5 deviation on right how much percent have you covered?

    • 9 months ago
  34. cnu115
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    and how did you get 0.37

    • 9 months ago
  35. dan815
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    do you know the answer already

    • 9 months ago
  36. cnu115
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    ????? 5*6/15=0.37 ????

    • 9 months ago
  37. dan815
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    whats the answer supposed to be

    • 9 months ago
  38. dan815
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    its 5.6 not 5 * 6

    • 9 months ago
  39. dan815
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    i cant help you if u arent answering my questions

    • 9 months ago
  40. cnu115
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    No. Idon't know the answer

    • 9 months ago
  41. dan815
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    then dont bother with stuff

    • 9 months ago
  42. dan815
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    first understand the graph

    • 9 months ago
  43. cnu115
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    I want to know more about this Z score

    • 9 months ago
  44. cnu115
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    Ok sir

    • 9 months ago
  45. dan815
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    the graph is pretty self explanatory and questions about it?

    • 9 months ago
  46. dan815
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    any questions?

    • 9 months ago
  47. cnu115
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    just a second sir,

    • 9 months ago
  48. cnu115
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    Now it is clear. But one question. May I ask

    • 9 months ago
  49. cnu115
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    Why did you divide by 15. It is only 14 parts. Right

    • 9 months ago
  50. cnu115
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    Sorry. Now I have fully understood.

    • 9 months ago
  51. cnu115
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    It is not the 14 parts. It is the area of that part.

    • 9 months ago
  52. cnu115
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    Thank you very much explaining in detailed manner

    • 9 months ago
  53. cnu115
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    Thanks for your patience and analysing for a lehman.

    • 9 months ago
  54. Musadiq
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    Mean 80 standard deviation 10 z=-0.67 X=73.3

    • 9 months ago
  55. Musadiq
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    mine answer is 73.3 marks min to get A

    • 9 months ago
  56. Musadiq
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    you have to take Z value -0.67

    • 9 months ago
  57. dan815
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    musadiq no try taking 0.67 Z

    • 9 months ago
  58. Musadiq
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    well table value is 0.67 that's lies at left side !

    • 9 months ago
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