Suppose the results of the analyses in Problem 15-17 are reported and criticized because the participants were not randomized to different diets, and that there may be other factors associated with changes in cholesterol. A third study is run to estimate the effect of the low-carbohydrate diet on cholesterol levels. In the third study, participants' cholesterol levels are measured before starting the program and then again after 6 months on the program. The data are shown below:
Before Program: 210 230 190 215 260 200
After 6 Months : 215 240 190 200 280 210
Is there a significant increase in cholesterol after 6 months on the low-carbohydrate diet? Run the appropriate test at a 5% level of significance.