A better drug? In a pilot study, a companys new cholesterol-reducing drug outperforms the currently available drug. If the data provide convincing evidence that the mean cholesterol reduction with the new drug is more than 10 milligrams per deciliter of blood (mg/dl) greater than with the current drug, the company will begin the expensive process of mass-producing the new drug. For the 14 subjects who were assigned at random to the current drug, the mean cholesterol reduction was 54.1 mg/dl with a standard deviation of 11.93 mg/dl. For the 15 subjects who were randomly assigned to the new drug, the mean cholesterol reduction was 68.7 mg/dl with a standard deviation of 13.3 mg/dl. Graphs of the data reveal no outliers or strong skewness. (a) Carry out an appropriate significance test. What conclusion would you draw? (Note that the null hypothesis is not H0:m1 m2 = 0.) (b) Based on your conclusion in part (a), could you have made a Type I error or a Type II error? Justify your answer.
Chapter2 Notes --- Displaying and Describing Categorical Data The Three Rules of Data Analysis Make a picture. Make a picture. Make apicture. Pictures … • Reveal things that can’t be seen in a table of numbers. • Show important features and patterns in the data. • Provide an excellent means for reporting findings to others Summarizing a Categorical Variable Example: The following...
