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Suppose the scores on a grammar quiz are normally distributed with a mean of 76 and a standard deviation of 8.

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

 

a. scores below 60

b. scores below 68

c. scores above 80

d. scores above 94

 Apr 10, 2019

Best Answer 

 #1
avatar+19675 
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(always good to commit to memory the values of the standard bell curve...as shown above)

Similar Q has been posted multiple times.    One standard deviation ABOVE 76 = 84    and has a z-score .8413   so approx 16% of the population is ABOVE this score  ....but that does not fit the answers......so look at the NEGATIVE z-score table for the value nearest .16  

Between -1.- and - 0.9 standard deviations represents this 16%  ...I'll just use -1.0

76 - 1.0(8) = 68        scores below 68 represent 16% of the scores

 Apr 10, 2019
edited by ElectricPavlov  Apr 10, 2019
edited by ElectricPavlov  Apr 10, 2019
 #1
avatar+19675 
0
Best Answer

(always good to commit to memory the values of the standard bell curve...as shown above)

Similar Q has been posted multiple times.    One standard deviation ABOVE 76 = 84    and has a z-score .8413   so approx 16% of the population is ABOVE this score  ....but that does not fit the answers......so look at the NEGATIVE z-score table for the value nearest .16  

Between -1.- and - 0.9 standard deviations represents this 16%  ...I'll just use -1.0

76 - 1.0(8) = 68        scores below 68 represent 16% of the scores

ElectricPavlov Apr 10, 2019
edited by ElectricPavlov  Apr 10, 2019
edited by ElectricPavlov  Apr 10, 2019

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