1. AP STATISTICS 4.2D Blocking and Matched Pairs Design

2. Housekeeping  Unit 1 Test Thursday and Friday (9/24 & 9/25)  Multiple Choice Thursday  FRQ Friday  These are timed tests—you must finish each section within the time allotted  Homework packets due ON ENTRY, Friday, 9/25

3. Team Time  Go over 4.2D HW

4. Opener: Doing Laundry Researchers want to test whether a new detergent for clothes that require hand- washing cleans better in warm or cold water. They decide to perform an experiment using numerous pieces of dirty laundry as the experimental units. The response variable is a cleanliness rating on a scale of 0 (very dirty) to 10 (very clean). Design a completely randomized experiment.

5. Opener: Doing Laundry How should researchers deal with the fact that light-colored clothes come cleaner in cold water? How could they ensure that after being assigned to a block, the clothes are randomly assigned a treatment?

6. The random assignment of experimental units to treatments is carried out separately within each block. Many piles of dirty laundry Assignment to blocks is NOT random Dark- colored clothing Light- colored clothing Random assignment Hot water Cold water Hot water Compare cleanliness Combine results Cold water

7.  Why do we block?  How does blocking bring control into the laundry experiment?

8. Control what you can, block what you can’t control, and randomize to create comparable groups.

9. Matched Pairs  Common type of randomized block design.  Create blocks by matching similar pairs of experimental units (blocks of size 2).  Use chance to decide which member of a pair gets the first treatment (random assignment of treatments within each pair).  Helps reduce the effect of variation among experimental units.  Sometimes each “pair” is one experimental unit who receives two treatments. The order of the treatments is randomized for each experimental unit.

10. Stand Up, Sit Down! LAB  Are standing pulse rates higher than sitting pulse rates?  If you received a black card, you will begin by sitting down. If you received a red card, you will begin by standing up.  When I tell you to begin, keep track of your heart rate. It will take one minute, so please focus. Record this number.  If you were standing, please sit down. If you were seated, please stand.  Again, we will record the number of heart beats in one minute.  Record your standing and sitting heart rates on your card.  Turn in your card

11. Homework  4.2D HW: Blocking and Matched Pairs Design