Question

Nonparametric: A small study is conducted to compare birth weight in babies born to mothers who do not smoke to those that smoke more than ½ pack/day. Is there a significant difference between birth weights due to maternal smoking status? Use the Mann-Whitney U test with a 5% level of significance. What is R₁ (non-smokers)?

Birth weights of infants in two groups of mothers. (Observed data)

Nonsmokers	Heavy Smokers (≥1/2 pack/day)
8.6	7.0
8.5	5.2
6.3	6.1
9.3	6.7
8.0	6.6
6.8	7.4
	4.9
	6.3

Answer 1

Nonparametric: A small study is conducted to compare birth weight in babies born to mothers who do not smoke to those that smoke more than ½ pack/day. Is there a significant difference between birth weights due to maternal smoking status? Use the Mann-Whitney U test with a 5% level of significance. What is R₁ (non-smokers)?

R1= 62.5

Calculated test value =2.19, P=0.0282 which is < 0.05 level of significance. Ho is rejected.

There is a significant difference between birth weights due to maternal smoking status.

Wilcoxon - Mann/Whitney Test
	n	sum of ranks
	6	62.5	Nonsmokers
	8	42.5	Heavy Smokers
	14	105	total
		45.00	expected value
		7.75	standard deviation
		2.19	z
		.0282	p-value (two-tailed)
No.	Label	Data	Rank
1	Nonsmokers	8.6	13
2	Nonsmokers	8.5	12
3	Nonsmokers	6.3	4.5
4	Nonsmokers	9.3	14
5	Nonsmokers	8	11
6	Nonsmokers	6.8	8
7	Heavy Smokers	7	9
8	Heavy Smokers	5.2	2
9	Heavy Smokers	6.1	3
10	Heavy Smokers	6.7	7
11	Heavy Smokers	6.6	6
12	Heavy Smokers	7.4	10
13	Heavy Smokers	4.9	1
14	Heavy Smokers	6.3	4.5