Descriptive Statistics — Mean, Median, Mode, Range, SD

GRE Quantitative · Axiom Academy

LESSON Descriptive Statistics — Mean, Median, Mode, Range, SD Five ways to summarize a dataset with a single number — and why the GRE tests which one you should trust. The mean (average) is the sum of all values divided by how many there are. Picture the dataset as weights sitting on a number-line beam: the mean is the exact point where a fulcrum placed underneath makes the beam perfectly level — push it too far left or right and the beam visibly tips. Sum of every value, divided by the count Dataset: 2, 4, 6, 8, 10 → Mean . The median is the middle value once the data is sorted from least to greatest. Watch the scattered points slide into sorted order, then peel away from the outside in — the outermost pair vanishes first, then the next pair, until only the middle survives. Odd count: the median is the single middle value. Even count: the median is the average of the two middle values. After sorting and peeling from both ends, one value survives: Median = 6 . Two values survive the peel: Median . 3. Mode — The Most Frequent Value The mode is the value that shows up most often. Watch each data point stack directly above its spot on the number line — the tallest stack marks the mode. A dataset can have one mode (unimodal), two (bimodal), or none at all if nothing repeats. Dataset: 2, 4, 4, 6, 8, 8, 8, 10 → 8 appears three times, more than any other value, so Mode = 8 . 4. An Outlier Drags the Mean, Not the Median

This is the written version of the interactive lesson above. See the full GRE Quantitative course.