Explain the purposes and formulas of the range, the interquartile range, and the semi- interquartile range Solution The semi-interquartile range is a measure of spread or dispersion. It is computed as one half the difference between the 75th percentile [often called (Q3)] and the 25th percentile (Q1). The formula for semi-interquartile range is therefore: (Q3-Q1)/2. Since half the scores in a distribution lie between Q3 and Q1, the semi-interquartile range is 1/2 the distance needed to cover 1/2 the scores. In a symmetric distribution, an interval stretching from one semi-interquartile range below the median to one semi-interquartile above the median will contain 1/2 of the scores.x range = vo² sin2 /g Where: vo = launch velocity = launch angle; sin2 = sin(2 * ) g = acceleration of grav.