M is a certain set of numbers with an average (arithmetic mean) of 10 and a standard deviation of 0.5. Q is a subset of M consisting of 5 terms. Exactly 80% of the numbers in Q are located within 2 standard deviations from the average of M. Which of the following could Q be? Choices
A) {3, 4, 5, 10, 11}  B) {3, 9, 10, 10, 11}  C) {3, 5, 9, 10, 16}  D) {1, 5, 7, 10, 11}  E) {5, 6, 7, 10, 12}
Exactly 80% of the numbers in Q, so 4 out of 5 numbers are from 10 - 2*{SD} = 9 to 10 + 2*{SD} = 11.   A. {3, 4,5, 10, 11} --&gt; only 2 numbers are in this range. Discard.   B. {3,9, 10, 10, 11} --&gt; 4 numbers are in this range. OK.   C. {3,5, 9, 10, 16} --&gt; only 2 numbers are in this range. Discard.   D. {1,5, 7, 10, 11} --&gt; only 2 numbers are in this range. Discard.   E. {5, 6, 7, 10, 12} --&gt; only 1 number is in this range. Discard.   Answer: {3, 9, 10, 10, 11}.
<result>B</result>
M is a certain set of numbers with an average (arithmetic mean) of 10 and a standard deviation of 0.5. Q is a subset of M consisting of 5 terms. Exactly 80% of the numbers in Q are located within 2 standard deviations from the average of M. Which of the following could Q be?