# B what do you measure c what baseline data should you

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B) What do you measure? C) What baseline data should you know about? D) What factors might confound this experiment? E) What would be the purpose of a randomization in this problem? Example 4: We wish to determine whether or not a new type of fertilizer is more effective than the type currently in use. Researchers have subdivided a 20-acre farm into twenty 1-acre plots. Wheat will be planted on the farm, and at the end of the growing season the number of bushels harvested will be measured. A) How do you assign the plots of land? B) What is the explanatory variable? C) What is the response variable? D) How many treatments are there? E) Are there any possible lurking variables that would confound the results? Homework: Day 1: pg 357-8 and 364-5 problems 5.33-40, 42

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Chapter 5: Producing Data When the objective is to compare more than two populations, the experimental design that decreases the variability within the samples is called a randomized block design. Block designs in experiments are similar to stratified designs for sampling. Both are meant to reduce variation among the subjects. We use different names only because the idea developed separately for sampling and experiments. Blocks allow us to draw separate conclusions about each block; for example, about men and women are their response to a medication. Blocking also allows more precise overall conclusions, because the systematic differences due to gender or some other characteristic can be removed A block is a group of experimental units that are similar is some way that affects the outcome of the experiment. In a block design, the random assignment of treatments to units is done separately within each block . Rather than treating the subjects as if they were in a single pool we split the subject population. Blocks are a form of control . They control the effects of some lurking variables (such as gender, weight, age, etc.) by bringing those variables into the experiment so they can be accounted/controlled for. Example 1 : An agronomist wishes to compare the yield of five corn varieties. The field, in which the experiment will be carried out, increases in fertility from north to south. Outline an appropriate design for this experiment. Identify the explanatory and response variables, the experimental units, and the treatments. If it is a block design, identify the blocks. Example 2: You are participating in the design of a medical experiment to investigate whether a calcium supplement in the diet will reduce the blood pressure of middle-aged men. Preliminary work suggests that calcium may be effective and that the effect may be greater for African-American men than for white or Hispanic men. Forty randomly selected men from each ethnic category are available for the study. Outline the design of an appropriate experiment. What kind of design is this? Can this experiment be blinded?
Chapter 5: Producing Data Example 3: An educational psychologist wants to test two different memorization methods to compare their effectiveness to increase memorization skills. There are 120 subjects available ranging in age from 18 to 71. The psychologist is concerned that differences in memorization capacity due to age will mask (confound) the differences in the two methods. What would

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