This is the third lesson in the Experimental Design Unit. Students will distinguish between an observational study and an experiment. They will identify experimental units, explanatory variables, response variables, and treatments. They will understand the necessity of comparison, randomization, and replication in a well-designed experiment. They will design experiments choosing the most appropriate design type: Completely Randomized, Block, or Matched Pairs. This lesson includes the answers, student copy of notes, and a SMART notebook file of the lesson. This lesson was designed to have the teacher lead the students through the note-taking process while incorporating examples for the students to try. I will be adding homework in August which will be at no additional cost to those who purchase before. I am also adding a video that will lead the students through the lesson for those teachers who flip their classroom or for absent students.