AP Statistics

Ch.4.2: Completely Randomized DesignDO NOW & Quick Quiz

DO NOW: Homework Review

From your Chapter 4 Packet, 4.2 Concept #2:1. What are the experimental units, explanatory

variable, treatments and response variable?Experimental units: Each of the 150 studentsExplanatory variable: classical musicTreatments: classical music, no musicResponse variable: test scores

DO NOW: Homework Review

2. What are potential lurking variables in this situation? Study time, tutoring, amount of sleep, etc.How could they affect the results? More studying, tutoring, and more sleep could lead to higher test scoresHow could we avoid their effects?Randomly assign students to groups so that the effects of lurking variables will be felt equally by all groups in the experiment.

DO NOW: Homework Review3. Describe a completely randomized design for Mr. Tyson’s experiment.

150 statistics students

Random Assignment

Group 1 75

students

Group 275

students

Treatment 1 classical

music

Treatment 2No music

Compare Test scores

DO NOW: Homework ReviewBONUS: How would you carry out the random assignment? Provide enough detail that a classmate could implement your procedure exactly as written.Random number method: Using an alphabetical list of the students, assign each student a number between 01 and 150. Use a calculator to randomly generate 75 unique numbers between 01 and 150. These students belong in the treatment group, where students will listen to classical music while studying. The other students will listen to no music.Hat method: Use 150 equally sized slips of paper. Label 75 of the slips “1” and 75 of the slips “2.” Then mix them up in a hat and have each student draw a number without looking. The students who draw “1” will be assigned to the group that listens to classical music while studying and the students who draw “2” will be assigned to the group that does not listen to music while studying.

Quick Quiz Solutions

1. What are the experimental units, explanatory variable, treatments and response variable?

Experimental units: Each of the 29 studentsExplanatory variable: small group discussionsTreatments: small group discussions, view video alone (no small group discussion)Response variable: performance evaluation

Quick Quiz Solutions

2. How can you avoid the effect of potential lurking variables in this experiment?Randomly assign students to treatment groups so that the effects of lurking variables will be felt equally by all groups in the experiment.

Quick Quiz Solutions3. Outline a completely randomized design for this experiment using a flowchart.

29 music students

Random Assignment

Group 1 15

students

Group 214

students

Treatment 1 small group

Treatment 2alone

Compare Evaluations

Quick Quiz Solutions2. Describe how you would carry out the random assignment. Provide enough detail that a classmate could implement your procedure exactly as written.Random number method: Using an alphabetical list of the students, assign each student a number between 01 and 29. Use a calculator to randomly generate 15 unique numbers between 01 and 29. These students belong in the treatment group, where students will meet in small groups. The other students will view the videos alone.Hat method: Use 29 equally sized slips of paper. Label 15 of the slips “1” and 14 of the slips “2.” Then mix them up in a hat and have each student draw a number without looking. The students who draw “1” will be assigned to the group that views the video and discusses it in small groups and the students who draw “2” will be assigned to the group that views the video alone and does not discuss it with a group.