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Nick designs a clinical trial to test a new anxiety medication by creating a control group and a treatment group. If he gives the medication to patients in the treatment group and not to the control ... group, some patients might find out that they're not being treated. To improve his study, Nick decides to give a sugar pill to the control group. The sugar pill is an example of a __________.  case control  confounding variable  variable of interest  placebo RATIONALE When no active treatment is given to the control group, we refer to this as the placebo. CONCEPT Placebo 2 The blood bank at a hospital has 1,200 units of blood, out of which 37% units are of blood group B+. A clinical researcher randomly selects 300 units of blood and finds that 33% of those are of blood group B+. To test his result, he randomly selects 200 units of blood and finds that 40% of those are of blood group B+. Which of the following is the reason there is a difference between the two percentages selected by the researcher?  Both samples suffered from non-response bias.  The samples were not random samples.  The sample sizes were both too small.  Random error; the numbers were different due to variability inherent in sampling. RATIONALE When sampling, there is always some variability that occurs. So, although the sample values are different, since they were randomly chosen, the differences are simply due to the variability that comes from sampling and not due to some systematic bias. CONCEPT Random and Systematic Errors 3 James participated in an archery competition. He was allowed four attempts and was supposed to hit the bullseye in the center of the board. If the figure shows the positions of James' arrows, which of the following would best classify the arrangement of arrows?  Low accuracy and low precision  High accuracy and high precision  Low accuracy and high precision  High accuracy and low precision RATIONALE The arrows are close to the center so they are accurate and they are also close to one another, so they are precise as well. CONCEPT Accuracy and Precision in Measurements 4 The following shows the Consumer Price Index (CPI) for the years 2000-2005. All of the values use a reference year of 1983. Which of the following is true about the CPI, based on the information?  $100 in 2002 would have been worth $189.70 in 1983.  $100 in 2003 would be equivalent to $183.70 in 1983.  $100 in 2000 would be equivalent to $194.50 in 2005.  $100 in 1983 would be equivalent to $178 in 2001. RATIONALE Recall the CPI gives us a measure of price changes over time and allows us to transform values in one year to another. The value of the CPI in the base year is 100. This means that for $100 in 1983 is equivalent to $178 in 2001. CONCEPT Index Number and Reference Value 5 An appliance store manager noted that the sales of home appliances contributed 74% of the store's profits in the year 2010 and 82% in the year 2011. Of the following choices, which statement about home appliance sales is true?  Home appliance sales increased profits by 9.75%.  Home appliance sales increased profits by 9.75 percentage points.  Home appliance sales increased profits by 8%.  Home appliance sales increased profits by 8 percentage points. RATIONALE We can note that the absolute difference between 2010 and 2011 is 74% to 82% or 8 percentage points. [Show More]

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