http://www.ck12.org Chapter 15. Concepts of Statistics
http://www.youtube.com/watch?v=4eLJGG2Ad30 Khan Academy: Histogram
Guidance
It is often easier for people to interpret relative sizes of data when that data is displayed graphically. There are a few
common ways of displaying data graphically that you should be familiar with.
- Apie chartshows the relative proportions of data in different categories. Pie charts are excellent ways of
displaying categorical data with easily separable groups. The following pie chart shows six categories labeled
A−F. The size of each pie slice is determined by the central angle. Since there are 360◦in a circle, the size of the
central angleθAof categoryAcan be found by:
360 θA =Total number o f data points#data points in category A- Abar chartdisplays frequencies of categories of data. The bar chart below has 5 categories, and shows the
TV channel preferences for 53 adults. The horizontal axis could have also been labeledNews, Sports, Local News,
Comedy, Action Movies. The reason why the bars are separated by spaces is to emphasize the fact that they are
categories and not continuous numbers. For example, just because you split your time between channel 8 and
channel 44 does not mean on average you watch channel 26. Categories can be numbers so you need to be very
careful.