1. **State the problem:** Calculate the mean birth mass of babies born to mothers who drank alcohol and those who did not. 2. **Formula for mean:** The mean of a set of numbers $x_1, x_2, \ldots, x_n$ is given by $$\text{mean} = \frac{\sum_{i=1}^n x_i}{n}$$ where $n$ is the number of data points. 3. **Calculate mean for babies born to mothers who drank alcohol:** Data: $2.40, 2.21, 3.15, 2.49, 2.10, 1.99$ $$\text{mean} = \frac{2.40 + 2.21 + 3.15 + 2.49 + 2.10 + 1.99}{6}$$ $$= \frac{14.34}{6}$$ $$= 2.39$$ 4. **Calculate mean for babies born to mothers who did not drink alcohol:** Data: $4.14, 4.89, 4.12, 3.02, 5.08, 3.89$ $$\text{mean} = \frac{4.14 + 4.89 + 4.12 + 3.02 + 5.08 + 3.89}{6}$$ $$= \frac{25.14}{6}$$ $$= 4.19$$ 5. **Final answers:** - Mean mass from mothers who drank alcohol = $2.39$ kg - Mean mass from mothers who did not drink alcohol = $4.19$ kg These means represent the average birth mass for each group, showing babies born to mothers who did not drink alcohol tend to have higher birth mass on average.