Repeated measures, Find another area of research. Decide what n you can afford. What is the purpose of Design of Experiments?

Repeated measures, Find another area of research. Decide what n you can afford. What is the purpose of Design of Experiments? To find out what causes our responses in the fewest possible experiments. We run an experimental design with four factors -- Temperature, Pressure, Speed, and Processing Time. Our analysis table gives a p-value of 0.01 for Pressure -- all other effects have large pvalues -- larger than 0.25. What does this all mean?