Chapter 11.2, Problem 40E

To determine

To explain which treatment seems to be most effective and least effective.

Answer to Problem 40E

The “Both” is most effective and “Placebo” is least effective treatment.

Explanation of Solution

Given:

		Having strock	Having no stroke	Total
Placebo	Observed	250	1399	1649
	Expected	205.81	1443.19	1649.00
	(O - E)² / E	9.49	1.35	10.84
Aspirin	Observed	206	1443	1649
	Expected	205.81	1443.19	1649.00
	(O - E)² / E	0.00	0.00	0.00
Dipyridamole	Observed	211	1443	1654
	Expected	206.44	1447.56	1654.00
	(O - E)² / E	0.10	0.01	0.12
Both	Observed	157	1493	1650
	Expected	205.94	1444.06	1650.00
	(O - E)² / E	11.63	1.66	13.29
Total	Observed	824	5778	6602
	Expected	824.00	5778.00	6602.00
	(O - E)² / E	21.22	3.03	24.24
		24.24	chi-square
		3	df
		2.22E-05	p-value

The treatment Both is most effective as the expected frequency 205.94 is higher than the observed frequency 157. That is the expected frequency deviates most from the observed frequency. The least effective treatment is Placebo as the expected frequency is lower than the observed frequency.