Chapter 11.2, Problem 42E

To determine

To find: the individuals’ components for the chi-square statistic and cell contributed the most to the final result.

Explanation of Solution

Formula used:

  ${\chi }^2={\displaystyle \sum \frac{{\left(O-E\right)}^2}{E}}$

Calculation:

Observed counts

	Stroke	No stroke
Placebo	250	1399	1649
Aspirin	206	1443	1469
Dipyridamole	211	1443	1645
Both	157	1493	1650
	824	5778	6602

Expected counts are

	Stroke	No stroke
Placebo	250.8128	1443.1872	1649
Aspirin	205.8128	1443.1872	1649
Dipyridamole	206.4368	1447.5632	1645
Both	205.9376	1444.0624	1650
	824	5778	6602

The chi-square statistic is

  $\begin{array}{c}{\chi }^2=\frac{{\left(250-205.8128\right)}^2}{205.8128}+\frac{{\left(206-205.8128\right)}^2}{205.8128}+\mathrm{...}\\ \mathrm{...}+\frac{{\left(1443-1447.5632\right)}^2}{1447.5632}+\frac{{\left(1493-1444.0624\right)}^2}{1444.0624}\\ =9.487+\mathrm{.....}+0.014+1.658\\ =24.243\end{array}$

The biggest chi-square subtotal for the placebo have been collected. And both. And both. This means that together the two drugs would strengthen Comes and therefore treatment (if not side effects) should be used Too meaningful).