Q1: What does it mean if the Mean Absolute Deviation is zero?
A: A MAD of zero indicates zero variability across the dataset. Every single recorded value is identical to the mean (for example, scores of 15, 15, 15, and 15). There is no spread whatsoever.
Q2: Can the MAD ever be a negative number?
A: No. Because the metric relies entirely on absolute values, measuring the physical distance of data points from the center along a number line, MAD can only ever be positive or zero.
Q3: How do I tell if a difference between two groups is significant on i-Ready?
A: Compare the difference between their means to their MAD values. If the difference between the two means is greater than twice the MAD, the distributions show minimal overlap, signaling a clear, meaningful performance gap between the groups.
