$3.$ Are experimental studies involving randomization always preferred over nonrandomized studies? Why or why not? $4.$ Name at least two reasons a factorial design may be useful in a clinical trial. $5.$ Describe a limitation of using a run$-$in period in an intervention study. $6.$ Describe the placebo effect. $7.$ Does the within group design provides more or less control over confounders than the between$-$group design. Why? $8.$ Describe the four phases of clinical trials. Also describe what is the goal of each phase? $9.$ Blinding is using in Randomized Controlled Trials.a$.$ Describe the difference between a single$-$blind study and a double$-$blind study? b$.$ What is the purpose of conducting a double$-$blind study? $10.$ Design your own randomized controlled trial using the six steps given in the chapter.