Data Analysis & Statistics

The four summary statistics, what each one really measures, and the reverse problems the GAT-E loves.

Extract the right number from a data display and combine values without falling for the common traps.

Probability as favourable-over-total, the complement shortcut, and how to combine simple events.

Count arrangements and choices by multiplying options stage by stage — the foundation of counting questions.

Average groups of different sizes correctly — the simple average is a trap when the groups are unequal.

Read counts from a frequency table and compute the mean by weighting each value by how often it occurs.

Decide whether order matters, then count selections correctly — the distinction that trips up most counting questions.

Count overlapping groups without double-counting, using the two-set formula and the "fill the middle first" rule.

Multiply along a sequence of events and adjust the pool when draws are made without replacement.

Measure how spread out data are, and predict how an outlier shifts the mean, median, and range.

Read growth, decline, and the steepest change from a line graph, and compute percent change over time.