Math 143 C/E, Spring 2001
IPS Reading Questions
Chapter 9, Section 1 (up to ``Beyond the basics", p. 632)



  1. How is this material on inference for 2-way tables related to and an extension of the 2-proportion inference procedures we learned in Section 8.2?















  2. Just like when we used the normal approximation to a binomial distribution, the chi-square distribution is only approximately accurate and should be used with attention paid to whether it will give a close approximation in a given setting. What does the text say are ``safe" situations (ones where the chi-square test should be relatively accurate)?








  3. In what sense should a certain count in a cell be expected? To date, I have provided no justification for the term ``expected count", let alone a reason behind the formula. Try this exercise, forgetting any formula that you know. Below is a 2-way table where all of the individual cells have been left blank. The only information you have are the marginal distributions. Operating under the assumption that the two populations (columns) are no different (that is, that they have the same conditional distributions), try to fill in the counts for each cell. (Note: the totals should work out for both columns and rows.)
    Gender
    Smoking Status Female Male Total
    Non-smoker 261
    Smoker 37
    Total 175 123