## 
##  Shapiro-Wilk normality test
## 
## data:  dat$Adiponectin
## W = 0.97262, p-value = 0.009439

Although the variable looks normal (bell curve); P value from Shapiro-Wilk normality test is 0.0094. Suggesting Wilcoxon test might be more appropriate.

## 
##  Welch Two Sample t-test
## 
## data:  Adiponectin by Group
## t = -1.613, df = 116.47, p-value = 0.1095
## alternative hypothesis: true difference in means is not equal to 0
## 95 percent confidence interval:
##  -3289.3102   336.4595
## sample estimates:
##    mean in group Case mean in group Control 
##              9336.351             10812.777
## 
##  Wilcoxon rank sum test with continuity correction
## 
## data:  Adiponectin by Group
## W = 1688.5, p-value = 0.08597
## alternative hypothesis: true location shift is not equal to 0

P value from Wilcox test is 0.086; Suggesting bordline significance between case and control.

## [1] "p value from trend test = 0.1612"

I also tried to divide Adiponectin level into quartiles. P value from trend test is 0.1611.