Discussion:
Q1. The mean lifetime for cardiac stents is 8.9 years. A medical device company has implemented some improvements in the manufacturing process and hypothesizes that the lifetime is now longer. A study of 40 new devices reveals a mean lifetime of 9.7 years with a standard deviation of 3.4 years. Is there a statistical evidence of a prolonged lifetime of the stents? Run the test at a 5% level of significance.
Q2. The Table below displays descriptive statistics on subjects involved in a clinical trial. Are any of the characteristics significantly different between groups? Justify briefly.
New Compound Placebo p-value
Mean age (years) 47.2 46.1 0.7564
Men (%) 44 59 0.0215
Mean educational level (years) 13.1 14.2 0.6898
Mean annual income $36,560 $37,470 0.546
Mean body mass index (BMI) 24.7 25.1 0.0851