Question

S-Adenosyl-l-methionine (SAMe) is a dietary supplement used to treat depression.

A study randomly assigned smokers who wanted to quit smoking to one of three groups: a low dose of SAMe, high dose of SAMe, or a placebo.

After 8 weeks of treatment and behavioral smoking cessation intervention, smoking abstinence was assessed biochemically.

Here are the findings:

	Abstinent	Still smoking	TOTALS
Placebo	7	33	40
Low-dose SAMe	7	33	40
High-dose SAMe	5	35	40
TOTALS	19	101	120

The component of the chi-square statistic for the cell of subjects abstaining from smoking in the placebo group is about?

	A.	6.33.
	B.	0.0034.
	C.	0.07.
	D.	33.337.

Answer 1

Chi-square statistic for the cell of subjects abstaining from smoking in the placebo group

= (O - E)² / E

where O is the oberved value in the cell of subjects abstaining from smoking in the placebo group

From the table, O = 7

E is the expected value in the cell of subjects abstaining from smoking in the placebo group

E = (Total subjects in Placebo group) * (Total Subjects in Abstinent group) / Total Subjects

= (40 * 19) / 120 = 6.33

Chi-square statistic for the cell of subjects abstaining from smoking in the placebo group

= (7 - 6.33)² / 6.33

= 0.07

The correct answer is C. 0.07