Greek ‘kyrtosis,’ meaning convexity. Measure of relative data value concentration in the center versus in the tails of a frequency distribution . Flatness or peakedness reflects concentration. A normal distribution has a kurtosis of 3. Higher kurtosis distributions show fatter tails with more extreme values. This is ‘leptokurtosis’. Lower kurtosis show fatter middles, less fewer extreme values. This is ‘platy kurtosis’. Refer to convexity.