两个配对的 t 检验 p 值 = NA 和 t=NaN

Question

我想做以下配对 t 检验：

str1<-' ENSEMBLE 0.934 0.934 0.934 0.934 '
  str2<-' J48 0.934 0.934 0.934 0.934 '

  df1 <- read.table(text=scan(text=str1, what='', quiet=TRUE), header=TRUE)
  df2 <- read.table(text=scan(text=str2, what='', quiet=TRUE), header=TRUE)

t.test ( df1$ENSEMBLE, df2$J48, mu=0 , alt="two.sided", paired = T, conf.level = 0.95)

我得到以下结果：

Paired t-test

data:  df1$ENSEMBLE and df2$J48
t = NaN, df = 3, p-value = NA
alternative hypothesis: true difference in means is not equal to 0
95 percent confidence interval:
 NaN NaN
sample estimates:
mean of the differences 
                      0

为什么我会得到它？

Answer 1

因为数据完全一样

df2[1,1] <- .935

t.test ( df1$ENSEMBLE, df2$J48, mu=0 , alt="two.sided", paired = T, conf.level = 0.95)

Paired t-test

data:  df1$ENSEMBLE and df2$J48
t = -1, df = 3, p-value = 0.391
alternative hypothesis: true difference in means is not equal to 0
95 percent confidence interval:
-0.0010456116  0.0005456116
sample estimates:
mean of the differences 
           -0.00025

Answer 2

你的两个向量完全一样。两组都没有差异，因此没有标准误差。所以你的答案是不确定的

两个配对的 t 检验 p 值 = NA 和 t=NaN

Two paired t-test p-value = NA and t=NaN

r

p-value