Composite decking is increasingly popular, as it requires little maintenance. Options include polyethylene (with an average cost per square foot of $7.82), polypropylene (average cost per square foot, $8.68) and polyvinyl chloride or PVC (average cost per square foot, $7.50 hollow core, $9.48 solid core.) Pros. Composite materials are very durable, and won't splinter or rot.
Two-sample t-tests for a difference in mean involve independent samples or unpaired samples. Paired t-tests are a form of blocking, and have greater power than unpaired tests when the paired units are similar with respect to noise factors that are independent of membership in the two groups being compared.
Paired Samples t Test. The Paired Samples t Test compares two means that are from the same individual, object, or related units. The two means typically represent two different times (e.g., pre-test and post-test with an intervention between the two time points) or two different but related conditions or units (e.g., left and right ears, twins).