Midterm 1A practice

A true b false 2 a confounding variable is a variable

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a. TRUE b. FALSE 2. A confounding variable is a variable not accounted for in a study but can influence the outcome. a. TRUE b. FALSE 3. When using regression, the X variable must be quantitative. a. TRUE b. FALSE 4. A set of data has 10 negative numbers and 4 positive numbers. Which is true? a. The IQR is a negative number b. The mean is a negative number c. The median is a negative number d. Can’t tell without the actual data set 5. If you have an experiment containing only one factor, the treatments and levels are the same. a. TRUE b. FALSE 6. r 2 tells you what percentage of the Y values are correctly predicted by X. a. TRUE b. FALSE 7. In 1993, the median age of brides in Ohio was 27.0 years. From this we know that most brides were around 27 years old. a. TRUE b. FALSE 8. The interquartile range is the average distance between the quartiles of a data set. a. TRUE b. FALSE 9. If the slope of the regression line is 1, the correlation between X and Y equals 1. 10. If you know the standard deviation you can figure out what the mean is. 11. Differences appear smaller in a histogram by using larger increments on the Y axis. a. TRUE b. FALSE 3

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12. An influential point always has a large residual. For questions 13-15 use the following boxplot:. 14 12 10 8 6 4 2 0 Number of sick days taken by employees at Company X 13. The boxplot above shows the data is skewed __________. a. LEFT b. RIGHT 14. Less than half of the employees took 11 or more sick days. a. TRUE b. FALSE 15. The label on the vertical axis of the above boxplot should be: a. Number of sick days b. Number of employees c. Percentage of employees d. Can’t tell without more information 16. Suppose the standard deviation of a data set is 5. If you add 10 to every number in the data set, the new standard deviation will still be 5. 17. A survey of 100 randomly selected students was found to have 40 males and 60 females. Of the 40 males, 30 of them stayed up late the night before an exam (75%). Of the 60 females, 50 of them stayed up late (83%). However, since you didn’t use a stratified random sample to collect this data, the results are biased toward females.
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