A humanities professor assigns letter grades on a test according to the followin

Question

A humanities professor assigns letter grades on a test according to the following scheme. A: Top 12% of scores B: Scores below the top 12% and above the bottom 62% C: Scores below the top 38% and above the bottom 17% D: Scores below the top 83% and above the bottom 6% Bottom 6% of scores Scores on the test are normally distributed with a mean of 70.3 and a standard deviation of 9.4. Find the minimum score required for an A grade. Round your answer to the nearest whole number, if necessary Answer Tabies Key Standard Normal Table 0 to z Submit ©2017 Hawkes Learning ype here to search 0

Explanation / Answer

The A score is got for top 12% of the scorers i.e. Z for .88 cumulative area.

Hence, Z = 1.175 for .88 cumulative area under the curve, hence,

Mean = 70.3
Stdev = 9.4

So, The top 12% score is Mean + Z*Stdev = 70.3 + 9.4*1.175 = 81.345

Hence, the minimum score required for an grade A is 81.345 or 81 ( rounding off to the nearest whole number)

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