Grouped Data Median Press Ctrl-A ©2009 – Not to be sold/Free to use Stage 4 Year 9

Grouped Data In grouped data: Data classes must not overlap. Intervals must be of equal size. They are used for a large range of scores. A class centre (cc) is calculated by averaging the end points.

3 Cumulative Frequency Histogram/Polygon Histogram Polygon xfCumulative Frequency cf cf x Ogive

4 Median cf x % 100% 0% 50% Median=2.1 for continuous data Median=2 for discrete data

5 Class Grouped Data – The Median Class Centre cc Tallyfcf There are 20 scores. Therefore the median is the 10 th and 11 th scores. 10 th = th = 22 Median = = 19.5 Σf=Σf= 20

6 Grouped Data – The Median cc f cf |2|2 |7|7 | 12 | 17 | 22 | 27 | 32 | 37cc cf Cumulative Frequency Histogram Cumulative Frequency Polygon ‘Ogive’ Median Median (rounds up) = 22