paired_sample_t-test
> data(anorexia, package="MASS") # weight gain (lbs.) in anorexic women > attach(anorexia) > str(anorexia) 'data.frame': 72 obs. of 3 variables: $ Treat : Factor w/ 3 levels "CBT","Cont","FT": 2 2 2 2 2 2 2 2 2 2 ... $ Prewt : num 80.7 89.4 91.8 74 78.1 88.3 87.3 75.1 80.6 78.4 ... $ Postwt: num 80.2 80.1 86.4 86.3 76.1 78.1 75.1 86.7 73.5 84.6 ... > ft = subset(anorexia, subset=(Treat=="FT")) # just the family therapy threatment > ft Treat Prewt Postwt 56 FT 83.8 95.2 57 FT 83.3 94.3 58 FT 86.0 91.5 59 FT 82.5 91.9 60 FT 86.7 100.3 61 FT 79.6 76.7 62 FT 76.9 76.8 63 FT 94.2 101.6 64 FT 73.4 94.9 65 FT 80.5 75.2 66 FT 81.6 77.8 67 FT 82.1 95.5 68 FT 77.6 90.7 69 FT 83.5 92.5 70 FT 89.9 93.8 71 FT 86.0 91.7 72 FT 87.3 98.0 > detach(anorexia) > rm(anorexia) > t.test(ft$Prewt, ft$Postwt, paired=T) Paired t-test data: ft$Prewt and ft$Postwt t = -4.1849, df = 16, p-value = 0.0007003 alternative hypothesis: true difference in means is not equal to 0 95 percent confidence interval: -10.94471 -3.58470 sample estimates: mean of the differences -7.264706 >
> t.test(ft$Postwt-ft$Prewt, mu=0, data=ft) One Sample t-test data: ft$Postwt - ft$Prewt t = 4.1849, df = 16, p-value = 0.0007003 alternative hypothesis: true mean is not equal to 0 95 percent confidence interval: 3.58470 10.94471 sample estimates: mean of x 7.264706 >
paired_sample_t-test.txt · Last modified: 2017/05/17 13:04 by hkimscil