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.
Therefore the number of data points will be the same.If you run a number of samples on Machine A and then a different number of samples on Machine B then each group is independent and do not have to be the same number. If all assumptions are met, you can then use a 2 sample t test. Oh, Mr. Darth: Only if the characteristics being created by machine B DEPEND on the characteristics being created by machine A. If not, then they are still independent.