Question

A small study (n=10) is designed to assess if there is an association between smoking in pregnancy and low birth weight. Low birth weight babies are those born less than 5.5 pounds. The following data represent the birth weights, in pounds, of babies born to mothers who reported smoking in pregnancy and those who did not.

Mother smoked in pregnancy: 5.0, 4.2, 4.8, 3.3, 3.9
Mother did not smoke during pregnancy: 5.1, 4.9, 5.3, 5.4, 4.6

Is there a significant difference in birth weights between mother who smoked during pregnancy and those who did not? Use Excel showing all formulas and run the appripriate test at a 5% level of significance.

Answer 1

For the data given, following is the result of the paired t-test performed using excel:

Let's denote the group in which mothers smoked as 1 and other as 2.

We have the following hypotheses:

H0: 1 = 2

Ha: 1 < 2

So this is a left tailed t-test.

The p-value is shown in green. Since p < 0.05, this means we have to reject the null hypothesis.

So,

Yes there is a significant difference in birth weights between mothers who smoked during pregnancy and those who did not.