Data Analysis Summary

GRE Quantitative · Axiom Academy

SUMMARY Unit Summary: Data Analysis A full recap of statistics, chart reading, probability, counting, and distributions — everything this unit covered, in one place. Mean, median, and mode each describe the "center" of data differently — pick median over mean when outliers or skew are present, since mean is pulled toward extreme values and median isn't. Standard deviation measures spread, not location: adding the same constant to every value leaves SD unchanged, while multiplying every value by k scales SD by |k| . Every chart and data interpretation set rewards the same 30-second habit before computing anything — read the title, axes, units, and footnotes first, or you'll answer the wrong question correctly. "At least one" probability problems are almost always faster through the complement: . Permutations count arrangements where order matters; combinations count selections where it doesn't — the GRE tests whether you can tell the two apart, not just whether you know the formulas. The normal distribution's 68-95-99.7 rule converts "how many SDs from the mean" directly into a percentile or proportion, which is how the GRE tests it. Core Concept Descriptive Statistics Mean, median, mode, range, and standard deviation each summarize a dataset a different way. The weighted mean matters whenever groups being combined have different sizes — a straight average of group averages is wrong unless every group is the same size.

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