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anonymous

  • one year ago

WILL FAN AND MEDAL The grades on the last art exam had a mean of 75%. Assume the population of grades on art exams is known to be distributed normally, with a standard deviation of 7%. Approximately what percent of students earn a score between 75% and 82%? 37.2% 84.1% 34.1% 50%

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  1. Hayleymeyer
    • one year ago
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    ohh snap, these problems! X_X

  2. anonymous
    • one year ago
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    I know that i need to use the z-Score formula, But now when it says "between %75 and %82" ZSCORE = \[z= \frac{ \mu - x }{ }\]

  3. anonymous
    • one year ago
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    whoops theres supposed to be a sigma under that

  4. Hayleymeyer
    • one year ago
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    hmmm

  5. Hayleymeyer
    • one year ago
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    @pooja195 help please? im not very good with this stuff! :)

  6. Hayleymeyer
    • one year ago
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    @Luigi0210 :)

  7. Hayleymeyer
    • one year ago
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    yay!! help has arrived!

  8. Luigi0210
    • one year ago
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    Don't know much stats, sorryy @imqwerty

  9. Hayleymeyer
    • one year ago
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    qwerty, you better help this kid! :)

  10. imqwerty
    • one year ago
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    damn this is statistics!!!

  11. Hayleymeyer
    • one year ago
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    @graysongraddylol do you still need help? :)

  12. anonymous
    • one year ago
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    Yes I do @Hayleymeyer

  13. Hayleymeyer
    • one year ago
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    okay, ima find you some help, cuz you seem nice

  14. Hayleymeyer
    • one year ago
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    @phi

  15. anonymous
    • one year ago
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    thank you :)

  16. Hayleymeyer
    • one year ago
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    anytime!

  17. Hayleymeyer
    • one year ago
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    @Nnesha

  18. anonymous
    • one year ago
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    @phi

  19. anonymous
    • one year ago
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    @freckles

  20. phi
    • one year ago
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    mean of 75%. standard deviation of 7% score between 75% and 82%? (it is a bit confusing because our measurements are percents (on a test)... and we also have percent (under a curve) ) but we want the area under the bell curve from 75% (the mean) and 82% (which is 1 std dev to the right of the curve) how much area is between the mean and 1 std dev from the mean do you know how to figure that out ?

  21. anonymous
    • one year ago
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    i have no clue what a standard deviation is :(

  22. Hayleymeyer
    • one year ago
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    yay! you got help!!

  23. phi
    • one year ago
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    do you know what a bell curve looks like?

  24. anonymous
    • one year ago
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    Like this.? |dw:1440706033076:dw|

  25. phi
    • one year ago
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    yes. and its symmetric (left side looks like right side) the exact middle is the mean

  26. anonymous
    • one year ago
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    |dw:1440706112012:dw|

  27. anonymous
    • one year ago
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    |dw:1440706140992:dw|

  28. phi
    • one year ago
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    the idea is the "area under the curve" is set = to one btw, in theory the "tails" never reach the x-axis half of the area is below the mean, and 1/2 of the area is above the mean

  29. anonymous
    • one year ago
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    Can't I solve this using the z-score formula.?

  30. phi
    • one year ago
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    yes, we use z-scores. But you need to get the basic ideas so far, you know (for example) |dw:1440706289865:dw|

  31. anonymous
    • one year ago
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    A friend of mine just told me it was 34.1% is that correct.?

  32. phi
    • one year ago
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    a "standard deviation" is a way to measure how far we are away from the mean you should memorize the area from -1 std dev (below the mean) to 1 std dev (above the mean) is 68.27% of the entire area

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  33. anonymous
    • one year ago
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    That is the emperical rule, Correct.?

  34. phi
    • one year ago
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    in other words, you should know this |dw:1440706585153:dw|

  35. phi
    • one year ago
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    there is a mathematical definition of the curve, and you can calculate the area. In the real world, measurements (for example, height of people), will form an almost perfect bell curve, and we can use the math to closely model the real world. back to your problem 75 is the mean 82 is 1 std dev above the mean we want this area |dw:1440706762063:dw|

  36. phi
    • one year ago
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    you are told the area from -1 to +1 is 68.27% your know the area is symmetric about the mean (in other words, 1/2 of that 68.27 is on the left side and 1/2 is on the right side of the mean) that is enough info to figure out how much area is from 0 to 1 (it's 1/2 of the area from -1 to 1)

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