Platelets are an important part of the blood because they cause the blood to clot when that is needed to stop bleeding. The drug eltrombopag (which we shall henceforth refer to as EL), was tried on patients with chronic liver disease who were about to be operated on to see whether it would prevent the need for transfusion of platelets during the surgery and shortly thereafter. Read the following excerpt from the abstract that accompanied this study, and answer the questions below. "Methods: We randomly assigned 292 patients with chronic liver disease of diverse causes and platelet counts of less than 50,000 per cubic millimeter to receive EL, at a dose of 75 mg daily, or placebo for 14 days before a planned elective invasive procedure that was performed within 5 days after the last dose. The primary end point was the avoidance of a platelet transfusion before, during, and up to 7 days after the procedure.
a. Identify the treatment variable and the response variable.
b. Was this a controlled experiment or observational study. Explain.
c. Do the sample percentages suggest that the drug was effective in reducing the chance of needing platelet transfusions?
d. What does the small p-value show?
e. Can you conclude that the use of EL reduces the chance of needing a platelet transfusion? Why or why not?