Mini-course 6: Tables of Counts - Things People Think

This mini-course from the Nuffield Exploratory Data Skills Project: Making Sense of Data is about how to deal with data in the form of counts. Such data, often transformed into percentages, are very common in newspapers as well as in technical reports and publicly available statistics. As a result of this mini-course students should learn to:

• be aware that not everything we would like to count can easily be counted
• simplify tables of counts by collapsing categories
• report results as rounded percentages
• choose the right totals from which to take percentages
• choose appropriately between different pictorial representations of counts and percentages
• use difference in percentages to report relationships
• find 'expected' frequencies for a model of no relationship and to look at standardised residuals
• cut a scatterplot on both axes to make a table of counts
• use differences in percentages and/or odds ratios to look at relationships in a table with more than two dimensions.
• use three dimensional bar charts to display such relationships.

The mini-course consists of six units

[b] Beliefs and attitudes[/b] is an introduction to some of the problems of counted data. The points it makes are simple but subtle, and it is intended to set the tone for work in later units.
[b] Women and work[/b] and[b] Women choosing to work [/b] form a related pair, the first on finding percentages and the second on making pictures of them.
[b] Different views of equality[/b] and [b] Attitudes to contraception [/b] both look at relationships between counts.
[b] Who would ban pornography?[/b] links the ideas to the more frequently taught methods based on models for expected frequencies and on chi-squared.

The teacher guide gives an overview of the mini-course.