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Warm-up 4.4 Designing Experiments

Warm-up 4.4 Designing Experiments. In order to assess the effects of exercise on reducing cholesterol, a researcher sampled 50 people from a local gym who exercise regularly and 50 people from the surrounding community who do not exercise

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Warm-up 4.4 Designing Experiments

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  1. Warm-up4.4 Designing Experiments In order to assess the effects of exercise on reducing cholesterol, a researcher sampled 50 people from a local gym who exercise regularly and 50 people from the surrounding community who do not exercise regularly. Each subject reported to a clinic to have their cholesterol measured. The subjects were unaware of the purpose of the study, and the technician measuring the cholesterol was not aware of whether the subject exercises regularly or not. • What type of study is this? • What are the units? • What are the conditions of interest being studied? 4) What are some possible error in the sampling that may affect the results?

  2. New Seats Wednesday!!! • Who NEEDS to sit in the front? • I like to give different people the chance to sit up front. • I also like to set up the tables differently so that different groups of people collaborate.

  3. Student of the day!Block 1

  4. Student of the day!Block 2

  5. H.W. Answers 4.2 E # 16, 18 and 19; 4.3 P#27, E#23 and 24 E16 a.A simple random sample will be difficult because if each cookie is a unit. So some how all cookies should be numbered to be randomly selected. A bag will be opened and wasted to collect data from a randomly selected cookie. b. Cluster sampling would involve randomly selecting an entire bag and collecting the data for all cookies in that bag. c. It all depends on time and money. If you don’t have much money but a lot of time cluster sampling would work. If you have a lot of money but not necessarily time, two-stage cluster sample would be better.

  6. 4.2 E 18 and 19 E #18. 600/30 means that you could potentially check every 20th page. But systematic sample has a random start, so use a random number generator to select a random page from 1 to 20 to start, and then check every 20th page from there. E#19 Since there are only 5 farms stratified sampling would be best. That way data is collected from all 5 farms and the average can predict the crop yield for all 5. Averages may be found for the random samplings within each strata to show more precise predictions of average crop yields.

  7. 4.3 P#27, E#23 and 24 The first factor is the brand of paper towel, with levels brand A and brand B. The second factor is wetness, with levels dry and wet. The response variable is the number of pennies the towel can hold before breaking. b. Randomize the assignment of wet or dry to each set of 20 towels (10 from each brand to each treatment) and the order of testing. There are four treatments: brand A wet, brand A dry, brand B wet, brand B dry. Write each treatment name on five slips of paper, then draw to determine the order. The experimental units are the 20 time towel combinations in which the tests will be performed. c. This is an experiment, although the results may not generalize beyond the towels tested unless it can be established that they are essentially The same as all towels of these brands. E#23 This is an example of an observational study. There is no treatment. You are only observing how long it takes the children to solve the puzzle. Then you are using the data to compare the results for grade levels. E#24 Observational study.

  8. More Examples of Parts of Experiments A nutritionist wants to study the effect of storage time (6, 12, and 18 months) on the amount of vitamin C present in freeze dried fruit when stored for these lengths of time. Vitamin C is a measured in milligrams per 100 milligrams of fruit. Six fruit packs were randomly assigned to each of the three storage times. The treatment, experimental unit, and response are respectively: A. A specific storage time, amount of vitamin C, a fruit pack. B. A fruit pack, amount of vitamin C, a specific storage time. C. Random assignment, a fruit pack, amount of vitamin C. D. A specific storage time, a fruit pack, amount of vitamin C. E. A specific storage time, the nutritionist, amount of vitamin C.

  9. More examples Some people claim they can get relief from migraine headache pain by drinking a large glass of ice water. Researchers enlist people that suffer from migraines. When a participant gets a migraine, he or she will take a pain reliever or a placebo. Half will also drink a large glass of ice water. Participants will then report the level of pain relief they experience. Identify which of the following are the factors and levels. • People that experience migraines • Levels of pain relief • Presence of Migraine • Pain reliever or placebo, ice water or no ice water

  10. 4.4 Designing Experiments to Reduce Variability

  11. Example of Designing an experiment You have been asked to select 20 participants for a drug trial that compares two different treatments for migraine headaches. The researcher have requested a block design (male/female) with control groups for each block. You have been given a list of people willing to participate in the trial, numbered 01 to 87. The first 42 people are female; the rest are male. Assume the the control group gets the standard treatment. The two treatments are then new treatment and standard treatment for the control group. Sketch a diagram for the design of this experiment In paragraph form, clearly explain how you will select the subjects for each block.   

  12. Using a random # Digit Table Beginning at line 123 of the random digits table (below), select the 10 women. Then begin at line 125 to select 10 men. (1 point) 123 58580 81507 27102 56027 55892 33060 41842 81868 124 71035 09001 43367 49497 72719 96758 27611 91596 125 96746 12149 37823 71868 18442 35119 62103 39244 126 96927 19931 36809 74192 77567 88741 48409 41903

  13. Matched Pair Experimental Design A matched pairs design is a special case of a randomized block design. It can be used when the experiment has only two treatment conditions; and subjects can be grouped into pairs, based on some blocking variable. Then, within each pair, subjects are randomly assigned to different treatments. The table to the right shows a matched pairs design for a hypothetical medical experiment, in which 1000 subjects each receive one of two treatments - a placebo or a cold vaccine. The 1000 subjects are grouped into 500 matched pairs. Each pair is matched on gender and age. For example, Pair 1 might be two women, both age 21. Pair 2 might be two men, both age 21. Pair 3 might be two women, both age 22; and so on.

  14. Quiz Directions • Start the quiz once you get it. • Answer ALL short response in complete sentences • Once you are finished, flip your quiz over in front of you and start the homework 4.3 #26 and 27; 4.4 E#34 and 38. Notebook Check next block 1) 4.1 2) 4.2 and 4.3 3) 4.4 25 pts each x 3 = 75 pts 15 pts for notes 10 pts for warm-up 25 definitions, 1 pt each for 25 pts Bring your textbook next time for the chapter review out of the textbook.

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