6: Give it a try

fish taking a lureOn the form below, you can put this all together. As you fill out each column, click on the button below it to check your numbers. By the way, this is where having a calculator will come in handy. As long as you use two significant digits in your calculations, the program will fill in additional digits for you.

Once again, recall that there were 42 Monday and Friday sick days out of 100.

observed (“o”) expected (“e”) (o-e) (o-e)2 (o-e)2/e
Monday/ Friday
Total 100 100    


So now you have calculated a number which is the chi-squared statistic for this test; it is 0.167. But what do you DO with it? You know that a big chi-squared statistic is bad (because it means that the data deviate a lot from the model) and a small chi-squared statistic is good (because it means the data doesn’t deviate). But how big is big, or how small is small?



detour signBefore we answer that question, we need to take a brief detour to discuss degrees of freedom. After that, we can finally answer the question, are Dilbert’s colleagues really out fishing on their long weekends?