Question

Medical researchers have noted that adolescent females are much more likely to deliver low-birth-weight babies than are adult females. Because low-birth-weight babies have a higher mortality rate, a number of studies have examined the relationship between birth weight and mother's age. One such study is described in the article "Body Size and Intelligence in 6-Year-Olds: Are Offspring of Teenage Mothers at Risk?"† The following data on maternal age (in years) and birth weight of baby (in grams) are consistent with summary values given in the article and also with data published by the National Center for Health Statistics.

Mother's age	15	17	18	15	16	19	17	16	18	19
Birth weight	2,259	3,423	3,241	2,618	2,867	3,357	2,940	2,565	3,168	3,543

Answer 1

To see whether there is a significant relationship between mother's age and birth weight of babies, the regression analysis is done in excel by following these steps,

The regression equation is defined as,

where the response variable Y = Birth Weight of babies and the explanatory variable X = Mother's age

Now, the regression analysis is done in excel by following steps

Step 1: Write the data values in excel. The screenshot is shown below,

Step 2: DATA > Data Analysis > Regression > OK. The screenshot is shown below,

Step 3: Select Input Y Range: 'Birth weight' column, Input X Range: 'Mother's age' column then OK. The screenshot is shown below,

The result is obtained. The screenshot is shown below,

Significance of Independent variable

From the regression output summary,

	P-value
Mother's age	0.000562	<	0.05	Significant

The P-value for the independent variable is less than 0.05 at a 5% significance level hence we can conclude that independent variables mother's age is statistically significant in the model.

Interpretation of Independent variable

	Coefficients
Mother's age	251.15

For a one year increase in the mother's age, the birth weight increases by 251.15.