Aresearcher wants to know if calcium is an effective treatment for lowering blood pressure. he assigns one randomly chosen group of volunteers to take calcium supplements; the other group will get a placebo. at the end of the treatment period, he measures the difference in blood pressure. the 50 members of the calcium group had blood pressure lowered by an average of 25 points with a standard deviation of 10 points. the 50 members of the placebo group had blood pressure lowered by an average of 15 points with a standard deviation of 8 points. to analyze this information we will use a answer a. two-sample t procedure. b. two-sample z procedure. c. matched pairs procedure.