An appraiser researching marketing time finds five competitive closed sales with days on market (DOM) of 18, 22, 31, 25, and 29 days. What is the mean DOM?
Correct Answer
B) 25 days
Mean = (18 + 22 + 31 + 25 + 29)/5 = 125/5 = 25 days. Keep the stated numerator, denominator and units distinct. Common errors: dividing by 4 instead of 5 gives 31 days; reporting the total days instead of the mean gives 125 days; reporting the shortest DOM gives 18 days.
Why This Is the Correct Answer
Option B is correct because the mean is (18 + 22 + 31 + 25 + 29) / 5 = 125 / 5 = 25 days. Dividing the total by the full count of five sales gives the arithmetic average DOM.
Why the Other Options Are Wrong
Option A: 18 days
Option A, 18 days, is just the shortest DOM in the set, not the average. The correct mean is 125 / 5 = 25 days.
Option C: 31 days
Option C, 31 days, comes from dividing the 125-day total by 4 instead of 5 (125 / 4 = 31.25, about 31). There are five sales, so the mean is 125 / 5 = 25 days.
Option D: 125 days
Option D, 125 days, is the total of all five DOM figures, not the mean. The total must be divided by 5 to get 25 days.
Sum, then count
For a mean, add the values up, then divide by how many items you added. Count the items twice before dividing.
How to use: Use this check on any average calculation to avoid dividing by the wrong number.
Exam Tip
Calculation distractors often include the raw total, a wrong divisor and one of the input figures; check that your answer is a true average of the full set.
Common Mistakes to Avoid
- -Dividing by one fewer than the number of sales
- -Reporting the total days instead of the average
- -Confusing mean DOM with median DOM
Concept Deep Dive
Analysis
This question tests a basic market-conditions calculation: the arithmetic mean days on market. Add the DOM of the five sales and divide by the number of sales, 5. The traps are using the wrong divisor, stopping at the total, or picking one data point instead of averaging.
Background Knowledge
Days on market measures how long listings take to sell and is a key indicator of market conditions. Appraisers often report the median DOM, but the mean is another measure of central tendency computed as the sum divided by the count. Rising DOM can suggest softening demand, while falling DOM can suggest a stronger market.
Real-World Application
Preparing a market conditions addendum, an appraiser pulls five competing closed sales from the MLS and averages their DOM to show how quickly similar homes are selling. He compares that figure with prior periods to judge whether marketing times are lengthening.
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