Mean of a Data Set
Question
Answer choices
- 46
- 11
- 10.2
- 8.2
- 9.2
E Correct answer: E) 9.2
Set up the problem carefully before computing. Add the numbers, then divide by how many there are. 46 ÷ 5 = 9.2.
Carry the arithmetic through one step at a time, double-checking signs and units. The ACT writes wrong answers to catch the most common slips, so an answer that "looks right" without verification is risky.
Plug the answer back into the original expression as a sanity check whenever the problem allows. If the substitution does not balance, you have made an arithmetic mistake earlier in the work.
The underlying rule
The mean is the sum divided by the count. Sum: 9 + 8 + 11 + 8 + 10 = 46. There are 5 numbers, so the mean is 46 ÷ 5 = 9.2.
Why each wrong answer is wrong
- A) 46: A common arithmetic or sign error leads to this value; carefully redo the calculation.
- B) 11: A common arithmetic or sign error leads to this value; carefully redo the calculation.
- C) 10.2: A common arithmetic or sign error leads to this value; carefully redo the calculation.
- D) 8.2: A common arithmetic or sign error leads to this value; carefully redo the calculation.
Study tip
Mean = sum ÷ count. Median = middle value when ordered. Mode = most frequent. The ACT loves to test whether you confuse them.
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