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.
The null hypothesis of no effect will be that the mean difference will be zero, i.e. . In this case, the alternative hypothesis states a positive effect, corresponding to. The test statistic is: where n is the sample size, , and is the standard error. The distribution of the test statistic under the null hypothesis follows a Student t-distribution.