1 The total project cost for a Trex deck ranges between $1,500 and $2,200 for a 250sf deck. 2  Trex Select of basic quality averages approximately $7/sf.  Trex Enhance of higher quality is approximately $8/sf.
When the hypothesized value is zero then there is a simple relationship between hypothesis testing and confidence intervals: If the interval contains zero then the null hypothesis cannot be rejected at the stated level of confidence. If the interval does not contain zero then the null hypothesis can be rejected.
Interpreting t [edit]. The null hypothesis for the test is that there is no difference between the mean scores of the two groups. If the confidence level is set to 95% you reject this with and accept the alternative hypothesis that the mean scores differ. The degrees of freedom for the t-test are given by N-2.