Accidents at Irongate

The Irongate Foundry, Ltd., has kept records of on-the-job accidents for many years. Accidents are reported according to which hour of an 8-hour shift they happen. The following table shows their accident report.

The union at the foundry wants to know whether accidents are more likely to take place during one hour of the shift rather than another. They are asking you what you think.

Do you think that more accidents are likely to take place during one hour of a shift over another?
If you said yes you would be hard pressed to prove yourself at this point, but continue on and be amazed!

Let's take a look at the data in graphical form and see if that helps us figure out when more accidents happen.

Does this histogram help in discerning when more accidents tend to happen?

The answer to that question is a resounding NO! It appears that staring at the numbers or at graphs of the numbers isn't going to sufficiently answer the question.

Statistics can help you answer the question that the union is asking. Many times in the real world you will come across situations just like this one where you have to make decisions about something occurring more often than another, or one product being better than another, or one candidate being favored over the other. A knowledge of the Chi-square statistic will help you.

Before you learn why the Chi-Square works and how to use it you must learn about some issues in statistics that you need to master before the chi-square makes any sense. Then you can help the Irongate Foundry and answer other questions such as one number more favored in your class, or is there a true best scorer on a basketball team.

The first thing you have to learn about is Fairness