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Chapter 31. Statistics

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What is the mode in the following data set:

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1, 1, 1, 1, 1, 1, 3, 4, 5, 5, 5, 5, 5, 7, 8, 8, 8?

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A. 1

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B. 3

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C. 4

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D. 5

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E. 8

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Mode is the most common value in the data set; in the above case, there are 6 value 1’s.

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What is the median in the following data set:

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1, 1, 1, 1, 1, 1, 3, 4, 5, 5, 5, 5, 5, 7, 8, 8, 8?

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A. 1

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B. 3

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C. 4

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D. 5

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E. 8

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Median is the value that divides the distribution of the data set. There are 17 numbers in the above data set; the 9th number (the middle number that divides the data set in half) in the above data set is 5. In case of even numbers of values in a data set, the mean of the 2 values that divide the data set would be the median. For example, the median of the data set 1, 1, 3, 5 would be (1 + 3)/2 = 2.

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A university research student wishes to study possible risk factors for disease X and decides to collect and compare the medical histories of 200 disease X patients within his institution in the last 10 years and compare with 200 other patients with similar age group, demography, and ethnicity but disease X free. What type of study is this?

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A. Case series

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B. Case-control

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C. Prospective cohort

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D. Randomized control studies

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This is a case-control study; the study is predefining disease X cases versus nondisease X case and trying to identify possible risk factors.

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What level of evidence would the above scenario (question 3) provide?

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A. Level I

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B. Level II-1

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C. Level II-2

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D. Level II-3

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E. Level III

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Evidence from case-control studies is considered Level II-2.

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A university researcher has developed a new screening test for disease ...

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