GRE Quant · Chapter Test
Descriptive Statistics — 25-Question Test
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Formula Reference Sheet
This chapter
Measures of centre
| Arithmetic mean | mean = (sum of values) / (number of values) |
|---|---|
| Sum from the mean | sum = mean × n |
| Median (odd n) | the single middle value once sorted |
| Median (even n) | average of the two middle values once sorted |
| Mode | the value(s) that occur most often |
Spread & weighting
| Range | range = greatest value − least value |
|---|---|
| Weighted mean | (Σ weightᵢ × valueᵢ) / (Σ weightᵢ) |
| Missing value | missing = (target mean × n) − (known sum) |
| New mean after adding x | (old sum + x) / (n + 1) |
GRE reference
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