In the data set [4,4,4,6,7,7,9], which statistic has the value 4?

• A. Mean
• B. Median
• C. Mode
• D. Range

Answer: (C)

The statistic being tested is the mode—the value that appears most often in a data set. Look at the data: 4 appears three times, 6 appears once, 7 appears twice, and 9 appears once. Since 4 occurs more times than any other value, the mode is 4. Here there is a unique mode, because no other value matches that highest frequency.

For contrast, the mean is the total sum divided by the count of values: (4+4+4+6+7+7+9)/7 = 41/7 ≈ 5.86, not 4. The median is the middle value when ordered; the ordered list is [4,4,4,6,7,7,9], so the median is 6. The range is the difference between the largest and smallest values: 9 - 4 = 5. So only the mode equals 4 in this dataset.