A component of cholesterol called high-density lipoprotein isknown to lower the risk of coronary heart disease. It is believedthat runners have increased HDL levels. The following data givedetails of an HDL study comparing male elite runners with a controlgroup of male nonrunners. At the α=0.05, test the claim that youngmale elite runners have a higher population mean HDL level thanyoung male nonrunners.
| sample | n | x̄ | s |
| elite runners | 20 | 56 | 12.1 |
| nonrunners | 72 | 49 | 10.5 |
