The sentence "alternative hypothesis: true difference in means is not equal to 0" is stating what the alternative hypothesis is and not that your particular difference in means is significantly different from zero. That sentence would appear (when you have a two-tailed test) no matter what the P-value might be.
Try t.test(Q,WD) t.test(Q,WD,alternative="two.sided") # Default t.test(Q,WD,alternative="less") t.test(Q,WD,alternative="greater") Jim Jim Baldwin USDA Forest Service -----Original Message----- From: r-sig-ecology-boun...@r-project.org [mailto:r-sig-ecology-boun...@r-project.org] On Behalf Of Michael Marsh Sent: Sunday, March 23, 2014 2:22 PM To: r-sig-ecology@r-project.org Subject: [R-sig-eco] report out by t.test I test differences between frequency of hits of exotic annual forbs in plots on two sites, Q and WD. > Q<-c(13,0,10,2,0,0,1,0,0,1,5) > WD<-c(0,0,1,0,0,0,0,0,0,0,1) > t.test(Q,WD) Welch Two Sample t-test data: Q and WD t = 1.9807, df = 10.158, p-value = 0.07533 alternative hypothesis: true difference in means is not equal to 0 95 percent confidence interval: -0.3342006 5.7887460 sample estimates: mean of x mean of y 2.9090909 0.1818182 The p-value is greater than 0.05, thus does not reach the 95% confidence level, yet the difference in means is reported as not equal to 0. Am I encountering a one-sided versus two sided comparison that I don't understand, or is ther another explanation? Mike Marsh _______________________________________________ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology This electronic message contains information generated by the USDA solely for the intended recipients. Any unauthorized interception of this message or the use or disclosure of the information it contains may violate the law and subject the violator to civil or criminal penalties. If you believe you have received this message in error, please notify the sender and delete the email immediately. _______________________________________________ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
