A randomized study compared death or severe neurodevelopmental impairment at age 2 years for preterm infants receiving either the drug erythropoietin (a neuroprotective agent) or placebo within 24 hours of birth [248]. Data are contained in the dataset erythro. Treatment group is saved under the variable name treatment, and outcome at age 2 years under the name outcome.

(a) Calculate point estimates for the outcome in each of the two treatment groups sepa- rately.

(b) Estimate and interpret the risk ratio, comparing patients who got erythropoietin to patients who got placebo.

(c) Construct a 95% confidence interval for the risk ratio. What does this confidence Interval tell you?

(d) At the 0.

05 level of significance, test the null hypothesis that the proportions of preterm infants who either die or experience neurodevelopmental impairment at age 2 years are the same in the two treatment groups. What is the p-value?

(e) What do you conclude?