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anonymous

  • one year ago

It's really easy just i don't understand it. Question: If the average score is 122 and the standard deviation is 35, what percentage of students scored between 52 and 122?

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  1. anonymous
    • one year ago
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    How do i figure out the percentage?

  2. Vocaloid
    • one year ago
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    convert 52 and 122 to z-scores using the formula z-score = (given value-mean)/standard deviation once you have the z-scores for 52 and 122, you have two options to find the answer one way would be to use a graphing calculator to find normalcdf(z-score for 52,z-score for 122) other method would be to use a z-table to find the decimal values for each z-score, then subtract (decimal value for 122 minus decimal value for 52)

  3. anonymous
    • one year ago
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    hmm

  4. anonymous
    • one year ago
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    but vocaloid i don't have the given value-mean/sx

  5. Vocaloid
    • one year ago
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    the problem gives you the mean and standard deviation, right? mean = 122 standard deviation = 35 z-score for 52: (52-122)/35 z-score for 122 (122-122)/35

  6. anonymous
    • one year ago
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    Wowow I am super dumb haha did not read the problem :/

  7. Vocaloid
    • one year ago
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    well, alternatively you could use the empirical rule if you recognize that 52 is two standard deviations below the mean

  8. anonymous
    • one year ago
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    Sorry about that

  9. Vocaloid
    • one year ago
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    no need to apologize

  10. Vocaloid
    • one year ago
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    |dw:1435071928611:dw|

  11. anonymous
    • one year ago
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    So i'm looking at -2 and 0 for z scores hmm

  12. anonymous
    • one year ago
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    And I got .0228 from the z table :D

  13. anonymous
    • one year ago
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    oh wait how do i find the z-score for each value? i had to use both to find one (-2,0)

  14. Vocaloid
    • one year ago
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    well, since -2 and 0 are integers that makes our work a bit easier well, the empirical rule tells us that the percentage is 34%+13.5% http://www.stat119review.com/_/rsrc/1351288349191/more-material/normal-distribution/empirical-rule/solving-empirical-rule-questions/emprulesmart.bmp

  15. Vocaloid
    • one year ago
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    but if you wanted to use a z-table, you would find the table value for 0, then the table value for -2, then subtract the two values

  16. anonymous
    • one year ago
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    oh ok

  17. anonymous
    • one year ago
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    thanks

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