1. The problem is to determine whether the data provides statistical evidence that the average birth weight of babies of SES mothers is not 120, given the hypotheses and significance level $\alpha = 0.05$. 2. The null hypothesis $H_0$ and alternative hypothesis $H_a$ are: $$H_0: \mu = 120$$ $$H_a: \mu \ne 120$$ This is a two-tailed test because the alternative hypothesis uses $\ne$ (not equal). 3. The significance level $\alpha = 0.05$ means we reject $H_0$ if the p-value is less than 0.05. 4. The statement says "Then they should fail to reject $H_0$," which means the p-value is greater than or equal to 0.05. 5. Since we fail to reject $H_0$, the data does not provide sufficient statistical evidence to conclude that the average birth weight differs from 120. 6. Therefore, the correct completion is: "The data does not provide statistical evidence that the average birth weight of babies of SES mothers is not 120." This means we do not have enough evidence to say the average birth weight is different from 120 at the 5% significance level.