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cnu115

  • 2 years ago

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?

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  1. dan815
    • 2 years ago
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    |dw:1373527655365:dw|

  2. cnu115
    • 2 years ago
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    standard deviation of 10

  3. dan815
    • 2 years ago
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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

  4. dan815
    • 2 years ago
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    look up the probability distribution graph numbers

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

  6. dan815
    • 2 years ago
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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

  7. dan815
    • 2 years ago
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    |dw:1373530622874:dw|

  8. cnu115
    • 2 years ago
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    Is it 21% with 0.8 standard deviation?

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

  10. dan815
    • 2 years ago
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    |dw:1373533594767:dw|

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

  12. dan815
    • 2 years ago
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    look at that chart and figure it out

  13. dan815
    • 2 years ago
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    |dw:1373533703309:dw|

  14. dan815
    • 2 years ago
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    its somewhre inbetween 0.5 and 1

  15. dan815
    • 2 years ago
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    id say around 0.75

  16. dan815
    • 2 years ago
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    so 0.75 of 10 = ? 7.5 marks

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

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

  19. dan815
    • 2 years ago
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    |dw:1373533813410:dw|

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

  21. dan815
    • 2 years ago
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    this will give u more accurate vlaue

  22. dan815
    • 2 years ago
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    |dw:1373533861018:dw|

  23. dan815
    • 2 years ago
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    |dw:1373533886859:dw|

  24. dan815
    • 2 years ago
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    |dw:1373533895795:dw|

  25. dan815
    • 2 years ago
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    |dw:1373533946389:dw|

  26. dan815
    • 2 years ago
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    |dw:1373533966949:dw|

  27. dan815
    • 2 years ago
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    |dw:1373533987799:dw|

  28. cnu115
    • 2 years ago
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    |dw:1373534025223:dw|

  29. cnu115
    • 2 years ago
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    what is this equation you have used

  30. dan815
    • 2 years ago
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    5.6/15

  31. dan815
    • 2 years ago
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    because

  32. dan815
    • 2 years ago
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    look at the chart

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

  34. cnu115
    • 2 years ago
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    and how did you get 0.37

  35. dan815
    • 2 years ago
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    do you know the answer already

  36. cnu115
    • 2 years ago
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    ????? 5*6/15=0.37 ????

  37. dan815
    • 2 years ago
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    whats the answer supposed to be

  38. dan815
    • 2 years ago
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    its 5.6 not 5 * 6

  39. dan815
    • 2 years ago
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    i cant help you if u arent answering my questions

  40. cnu115
    • 2 years ago
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    No. Idon't know the answer

  41. dan815
    • 2 years ago
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    then dont bother with stuff

  42. dan815
    • 2 years ago
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    first understand the graph

  43. cnu115
    • 2 years ago
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    I want to know more about this Z score

  44. cnu115
    • 2 years ago
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    Ok sir

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

  46. dan815
    • 2 years ago
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    any questions?

  47. cnu115
    • 2 years ago
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    just a second sir,

  48. cnu115
    • 2 years ago
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    Now it is clear. But one question. May I ask

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

  50. cnu115
    • 2 years ago
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    Sorry. Now I have fully understood.

  51. cnu115
    • 2 years ago
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    It is not the 14 parts. It is the area of that part.

  52. cnu115
    • 2 years ago
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    Thank you very much explaining in detailed manner

  53. cnu115
    • 2 years ago
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    Thanks for your patience and analysing for a lehman.

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

  55. Musadiq
    • 2 years ago
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    mine answer is 73.3 marks min to get A

  56. Musadiq
    • 2 years ago
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    you have to take Z value -0.67

  57. dan815
    • 2 years ago
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    musadiq no try taking 0.67 Z

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

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