Unit 4: Gathering Data LESSON 4-5 – MORE EXPERIMENTAL STUDIES ESSENTIAL QUESTION: WHAT ARE SOME OTHER FACTORS TO CONSIDER IN PLANNING AND EXECUTING AN EXPERIMENTAL STUDY? BCHS - PROBABILITY & STATISTICS

LEARNING OBJECTIVES QUESTIONS FOR LESSON 4-5 1)How can we perform MULTIFACTOR EXPERIMENTS? 2)What does it mean to use RANDOMIZED BLOCK DESIGN? 3)What will a MATCHED PAIR DESIGN do for our study? 4)How can CROSSOVER DESIGN be used in an experimental study?

Learning Objective 1: MULTIFACTOR EXPERIMENTS  A multifactor experiment uses a single experiment to analyze the effects of two or more explanatory variables on the response.  Categorical explanatory variables in an experiment are often called factors.  We are often able to learn more from a multifactor experiment than from separate one-factor experiments since the response may vary for different factor combinations and levels.

Learning Objective 1: MULTIFACTOR EXPERIMENTS Before we get all ‘statistical’ on you, think about fruit… What is the tastiest fruit? What is the easiest fruit to open/eat, no cutting/waste? Now what is the tastiest fruit that is also the easiest to open? See what we did there, we looked at multiple factors of fruit at the same time. How about the least tasty and most difficult to open fruit?

Does not necessarily represent the expressed tastes or views of Mr. Miller or Mr. Coots… (coconuts not able to be shown)

Learning Objective 1: MULTIFACTOR EXPERIMENTS REAL EXAMPLE A: A research team wants to examine the effectiveness of both Zyban and the nicotine patch in helping smokers quit. This is a ___ factor experiment. There are ___ different treatments. (think ‘combinations’) We assign experimental units to Treatment 1, 2, 3, or

Learning Objective 1: MULTIFACTOR EXPERIMENTS

Learning Objective 1: MULTIFACTOR EXPERIMENT EXAMPLE B: A research team gathers 60 undergraduate students, to view a 40-minute TV program that includes commercial ads for a soft drink. Some subjects will see a 30-second commercial; others will see a 90-second version. The same commercial will be shown either 1, 3, or 5 times during the program. What are the two factors for this experiment? How many treatment groups will there be? lengthrepetition amount 2 x 3 = 6

Learning Objective 1: MULTIFACTOR EXPERIMENT Factor 2: Repetitions 1 time3 times5 times Factor 1: Length 30 seconds ABC 90 seconds DEF Subjects in Treatment C for example, are assigned to watch a ___________________ repeated ___________ during the program. After viewing, all subjects then answer questions about their recall of the add, their attitude toward the commercial, and their intention to purchase the product. THESE ALL become the _________________. response variables 30-second version 5 times

Learning Objective 2: RANDOMIZED BLOCK DESIGN  A block is a set of experimental units that are grouped with respect to one or more characteristics.  A Randomized Block Design, RBD, is when the random assignment of experimental units to different treatments is carried out separately within each block.  So, we determine what blocking variable we feel will have an effect on the response, in order to make better comparisons of the treatments of interest.  Now we can be more confident that the results weren’t due to the blocking variable not being blocked.

Learning Objective 2: RANDOMIZED BLOCK DESIGN Experimental Study Motto: “CONTROL what you can…. BLOCK what you can’t control… and RANDOMIZE the rest.” – Professor Rob Tarrou

Learning Objective 2: RANDOMIZED BLOCK DESIGN  Why do we need RBD? Look at the graph above. The 1200 subjects are randomly assigned into groups. However, that means we could randomly end up with more male subjects in Group 1, or more elderly people in group 4. That will mess up our results…

Learning Objective 2: RANDOMIZED BLOCK DESIGN  Now we can be purposeful in blocking for ___________, by having an equal 600 and then randomly splitting and assigning the treatment groups. gender

What are all of these cartoon characters examples of? How similar is your pair?

Learning Objective 3: MATCHED PAIRS DESIGN  In a matched pair design, the subjects receiving the two treatments are somehow matched up by a similar trait/characteristic or are connected in some way.  One subject in the pair gets Treatment A and the other subject gets Treatment B. Results can then be compared better, because we know that the subjects had pre-existing similarities, or will act in similar ways during the treatment.  Essentially, we are reducing the effect of lurking variables that are difficult or impossible for us to even know about on the surface. (same gender/age, a husband/wife pair, have the same condition, etc.) (two 50 year old men living in the same city have similar sun exposure) (husband and wife pair have similar sleep and eating schedules)

Learning Objective 3: MATCHED PAIRS DESIGN

 You may have noticed that matched pair design is a form of RBD, but can only be used when there are two treatments to compare.  Randomness still need to be used in matching each subject with a treatment (not all the husbands should get the vaccine, while the wives get the placebo).  The difficult in this design is getting everyone matched up. You may have leftovers that then need to be left out of the study.

Learning Objective 3: MATCHED PAIRS DESIGN  You may have noticed that matched pair design is a form of RBD, but can only be used when there are exactly two treatments to compare.  Randomness is still need to be used in matching each subject with a treatment (not all the husbands should get the vaccine, while the wives get the placebo).  The difficulty in this design is getting everyone matched up. Figuring out how the criteria for matching is challenging and you may have leftovers that then need to be left out of the study.

Learning Objective 3: MATCHED PAIRS DESIGN EXAMPLE: Who would you put together for a matched pair design, where one person gets a newly developed nicotine patch and the other gets a placebo? SubjectGenderAgeWeightCigs per DayCareer 1 M Store Manager 2 F Cashier 3 M Retail Sales 4 F Stay Home Mom 5 M Banker

Learning Objective 4: CROSSOVER DESIGN  Crossover design is a form of matched pair design… minus the pair. Each subject ‘ crosses over ’ in treatment groups. You may be familiar with this type of crossover…. …and this type as well... But in experimental studies…

Learning Objective 4: CROSSOVER DESIGN  Each subject essentially becomes their own control group and takes both treatments in succession to one another.  You have to randomly assign the order of the treatments to each subject, because the first may have an impact on the second ( carryover effect ). * - well not ‘literally’ unless your study is on arm strength and projectile motion Less subjects are generally needed, because you are literally killing two birds with one stone*; every subject is participating in both treatments during the study.

Learning Objective 4: CROSSOVER DESIGN

SubjectMigraine Drug Placebo 1 ReliefNo Relief 2 Relief 3 No Relief 4 5 ReliefNo Relief 6 Relief Migraine drug was 67% effective (4/6), placebo was 33% effective (2/6) Subjects 2, 5, & 6 took the drug first, 1, 3, 4 took placebo first.

Learning Objective 4: CROSSOVER DESIGN  In order to use crossover design for medical trials and experiments, the subjects need to be chronic and stable.  This means the treatments should not result in total cures, only alleviation of the disease/condition and an improvement of quality of life.  If it isn’t chronic and Treatment A works, the subject won’t need Treatment B and our study is pointless. (asthma for example; we can help it, but can’t eliminate it) (just having a cold for example, the first treatment might make it go away, or the combination of Treatment A and Treatment B might affect the recovery)

Learning Objective 4: CROSSOVER DESIGN EXAMPLE: A research team wants to know if ACL replacement is more successful long-term using a pig patellar tendon or cadaver patellar tendon. They find 500 people who are scheduled for ACL replacement surgery within the next month and completely finance each person’s operation/recovery.  What might they block in randomized block design?  How might they match people up for matched pair design?  Is crossover design possible? How or why not? (more women have ACL tears than men, so not gender, maybe body weight) (similar athletic ability/sports participation, age, fitness levels) (unless both knees are blown, not possible; or we can tear it again for fun)