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suppose the scores on a history quiz are normally distributed with a mean of 73 and a standard deviation of 4.

Which group describes 16% of the population of history quiz scores?

 

scores below 65

scores below 75

scores above 77

scores above 81

 Apr 4, 2019
 #1
avatar+18754 
+2

Look at you grapefruit question....this is similar....can you try to get an answer?

 

Hint:   Look at negative z-score table for ~  16%  (.16)

 

 

...as an aside.....the answer choices do not include the correct answer.....You'll have to pick the closest one , I reckon.cheeky

 Apr 4, 2019
 #2
avatar+102355 
0

The z score closest to 16% appears to be ≈  -.99

 

So....we have that

 

raw scores -   mean

________________  <     -.99

  std. dev.

 

 

raw scores - 73

____________   <   -.99      multiply both sides by  4     

     4

 

raw scores - 73  <  -3.96       add 73 to both sides

 

raw scores <   69.04  ≈   70%  =  scores below 70

 

 

cool cool cool

 Apr 4, 2019
edited by CPhill  Apr 4, 2019

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