Practice Set 2

About This Set

Every question here takes two steps before the answer: a grouped table worked through class marks and step deviations, inclusive classes such as 20-29 widened to 19.5-29.5, a cumulative table turned back into class frequencies, a missing value found from a given mean, median or mode, or a list arranged before its quartiles are read. Watch three things in particular: the cumulative frequency in the median formula belongs to the class before the median class, $f_0$ is the class before the modal class and $f_2$ the one after it, and multiplying every value by $k$ multiplies the variance by $k^2$ but the standard deviation only by $|k|$. Give it 30 minutes. If 19 or more come out right, the grouped-table formulas are holding up and Practice Set 3 is next.