In a 2018 study, researchers investigated the effect of the drug alteplase in the treatment of stroke patients (Thomalla et al. 2018). Patients were randomly assigned to receive intravenous alteplase or a placebo. The patients’ neurological function was assessed 90 days after treatment. Of the 246 patients who received alteplase, 131 had a positive neurological outcome. Of the 244 patients who received a placebo, 102 had a positive neurological outcome.

a. Was this an observational study or a controlled experiment? Explain.

b. Find the percentage in each group that had a positive neurological outcome 90 days after treatment.

c. Researchers performed a test to determine if there was a significant difference in the proportion of positive neurological outcomes between the treatment and control groups. The p-value for the test is 0.003. Based on a 0.05 significance level, choose the correct conclusion:

i. Researchers have shown that alteplase may be an effective treatment for stroke patients.

ii. Researchers have not shown that alteplase may be an effective treatment for stroke patients.