Today's Agenda: 1. Hand back and go over Topic 4 Quizzes 2. Hand back and go over exit slips 3. Correct and collect Activities 5 7, 5 17 & 5 23 4. Activity 5 4 5. Activity 5 8. Activity 5 7. Topic 5 Preliminaries 8. Activity 5 5 9. Start Homework: Activities 5 9 & 5 11 Objectives: Students will be able to draw a flow chart for an experiment Students will be able to explain what a placebo is and why it is used. Students will be able to identify whether blindness is used in an experiment. Topic 5 Day 2 Homework #2: Activities 5 9 & 5 11 Saint John's Wort A study concluded that the herb Saint John'swort is no more effective than a placebo at relieving major depression. The study reported that it used a randomized, doubleblind, placebo controlled clinical trial on 200 patients. Patients' depression was measured using the Hamilton Rating Scale for Depression over the treatment period. Use this information to draw a flow chart for this clinical trial. 200 subjects with depression Random Assignment Treatment 1: received Saint John's wort (100 subjects) Treatment 2: received placebo (100 subjects) score on the Hamilton Rating Scale for Depression
The other day we learned that... An experiment can help us find out if one variable affects (or causes) another. Randomizing subjects into treatment groups will even out the variables that we are NOT interested in. (Especially those unrecorded variables that could affect the results of our experiment). Making a flow chart can help us understand how an experiment is set up. In Topic 4 we learned that... We want to control (or minimize) any bias present when we are collecting our data. Bias is bad! Today, we will learn... BIAS There are other kinds of bias can affect an experiment. We will learn how we can control those forms of bias. Activity 5 4: Botox for Back Pain a. Would you conclude that Botox is an effective treatment for back pain? Explain. No. It's not an experiment... everyone is receiving the same treatment; there is no comparison. b. Identify two ways in which this is an improvement over the original design. 1. There is a control group (half of the people received nothing). 2. Subjects were randomly chosen to be in the "treatment" or "nothing" groups. c. Identify a flaw in this design that would still prevent researchers from concluding that Botox causes a reduction in back pain, even if its group experiences much more pain reduction than the no treatment group? By providing one group with ANY treatment and the other group with NOTHING, the nothing group could end up feeling worse because nobody's helping them! They would be jealous or resentful of the group that is receiving something. d. How could we eliminate this confounding variable, creating a more effective study? We need to give everybody SOMETHING. Half of the people should get a placebo while the other half gets the actual medication.
Topic 5: Designing Experiments Vocabulary random assignment (5 1 & 5 3) = this generally creates even treatment groups by balancing out any confounding variables placebo (5 4) = a "sugar pill" with no active ingredients; it is used to eliminate any confounding psychological effects by the subjects placebo effect (5 4) = when subjects respond simply to receiving some kind of treatment blindness (5 4) = when subjects don't know if they are receiving the treatment or a placebo double blindness (5 4) = when both subjects and researchers don't know who is receiving the treatment or the placebo Activity 5 8: Treating Parkinson's Disease b. Explain what double blind means. Neither the doctors nor the patients know who is being implanted with the Spheramine and who is being implanted with the placebo. Why is it important in this study? It is human nature to WANT something to work! If the doctors knew who had the active medication and who had the placebo, they may be looking for improvements in the treatment groups' conditions. (We tend to see only what we want to see.) By using double blindness, we are allowing doctors and patients to be impartial and consistent with recording or reporting symptoms. c. Explain what randomized means. Researchers used an impartial way of deciding who would receive which treatment. Why is it important in this study? Randomizing is important because we want to evenly distribute any lurking variables that may be present, such as gender, severity of the patients' current condition, other physical conditions, etc. d. Explain what placebo controlled means. Some patients received the Spheramine implants and others received a placebo. Why is it important in this study? Because if there are any significant differences at the end of this study, we can attribute it to the Spheramine because that was the only variable that was different between the two groups. a. What does "sham" surgery mean? It means that in order to do the experiment, some patients had to receive the placebo. If these patients were not actually operated on, they would know that they had been assigned to receive the placebo. To eliminate the placebo effect, all patients had to undergo the same type of surgery and recovery to protect the blindness involved.
THE 3 PRINCIPLES of EXPERIMENTATION (and why we use them) 1. CONTROL reduces variability 2. REPLICATION verifies accuracy of experiment results 3. RANDOMIZATION reduces bias WAYS TO IMPROVE EXPERIMENTAL DESIGNS Blocking Matched Pairs Double Blind reduces variation due to the most obvious natural differences in subjects usually a person is compared to themselves (Pre and Post Test) reduces unintentional bias and allows researchers to be more objective when collecting data
Blocking Block Design A BLOCK is a group of experimental units or subjects that are known before the experiment to be similar in some way that is expected to systematically affect the response to the treatments. In a BLOCK DESIGN, the random assignment of units to treatments is carried out separately within each block.! A wise experimenter will form blocks based on the most important, unavoidable sources of variability among the experimental units. Blocking Example: DO NOT combine male and female results! random assignment
MATCHED PAIRS Matching the subjects in various ways can produce more precise results than simple randomization. The simplest use of matching is a MATCHED PAIRS DESIGN. This design compares just two treatments. The subjects are matched in pairs or a subject is compared to itself (often with a pre and post test).
"Are you sure this is what the statisticians call a double-blind experiment?" Activity 5 : AZT and HIV a. Explanatory Variable (and type) = AZT or placebo (CB) Response Variable (and type) = baby infected with HIV or not (CB) subjects = pregnant mothers infected withhiv b. Is this a survey, an observational study or an experiment? experiment; researchers are controlling the medication the mothers receive Draw a flow chart of this study: pregnant women infected with HIV (33) AZT (180) placebo RA (183) c. How does this study use comparison? Why? At the end of the experiment, we are able to make comparisons between the babies born to mothers who took AZT and the babies born to mothers who took the placebo. This is important because if there are any significant differences between the two groups of babies, we can attribute the difference to AZT (the only uncontrolled variable in the experiment). d. How does this study use random assignment? Why? e. How does this study use blindness? Why? baby infected with HIV or not The mothers are randomly assigned to receive either the AZT or the placebo. This is important because it will evenly distribute any lurking variables between the two groups of mothers. Because neither the mothers or the doctors don't know who received which medication, they can be more objective about the symptoms that are recorded along the way.
Topic 5 Preliminaries 1. How many letters can YOU memorize? 2. Record the results of your classmates: 21 15 24 21 21 15 3 15 21 19 4 17 7 3 14 20 18 20 1 14 4 10 14 17 1 0 4 Activity 5 5: Memorizing Letters a. Why is this an experiment and not an observational study? Because there was control involved. Mrs. Fruchter controlled who received which version of letters. b. Explanatory Variable (and type) = Version 1 (JKF) or Version 2 (JFKC) (CB) Response Variable (and type) = Number of letters memorized Flow chart: Statistics students (37) JFK (20) JFKC (17) RA c. How was random assignment implemented? Mrs. Fruchter shuffled the strips of paper and handed them out in no particular order. Why was it important? (Q) Number of letters memorized To even out any lurking variables. For example, if we had a couple of people with photographic memories, they should be evenly distributed by chance between the two groups. We will get to these tomorrow! d. How was blindness implemented? The students did not know what they were receiving and Mrs. Fruchter handed the papers out face down so she wouldn't know which papers students were receiving. Why was it important? So there wouldn't be any unintentional favoring by giving a student one version or the other on purpose. e. Use your graphing calculator and create comparative dotplots for the JFK data vs. the JFKC data. f. Does the data support the conjecture that those who receive letters in meaningful chunks tend to memorize more letters? g. Can we legitimately say that the meaningful chunks CAUSES people to memorize more letters? Why or why not?