Practice Questions for Data: distributions, connections and gatherings

Questions

1. What are the three conditions (provisions) for causality?

2. Immediately after the exam M&T, we determined of 11 randomly chosen students how many of the 40 questions they answered correctly. The results are presented in the stemplot below.

Determine the median.

3. What is the median of the scores 4-6-8-10-18?

4. What is the median of the following numbers: 8, 9, 14, 15?

5. The following five terms are used frequently to summarize the characteristics of a statistical variable: minimum, maximum, first quartile, third quartile, median. What is the right order, from small to large?

6. What does ‘error variance’ mean?

7. How can the standard deviation be computed from the variance?

8. To provide insight in the association between number of cigarettes smoked per day and the time needed to run 2 kilometers, you make a chart based on the data for a number of participants. Which variable do you put on the x-axis?

Answers

1. What are the three conditions (provisions) for causality?

• The variables should covary together

• The cause should precede the consequence

• The influence of other variables should be eliminated

2. Immediately after the exam M&T, we determined of 11 randomly chosen students how many of the 40 questions they answered correctly. The results are presented in the stemplot below.

Determine the median.

19

3. What is the median of the scores 4-6-8-10-18?

8

4. What is the median of the following numbers: 8, 9, 14, 15?

11.5

5. The following five terms are used frequently to summarize the characteristics of a statistical variable: minimum, maximum, first quartile, third quartile, median. What is the right order, from small to large?

Minimum, first quartile, median, third quartile, maximum

6. What does ‘error variance’ mean?

Error variance is the variance that can not be explained by the researcher, and thus is caused by measurement error and variables that are not examined by the researcher.

7. How can the standard deviation be computed from the variance?

By taking the square root of the variance.

8. To provide insight in the association between number of cigarettes smoked per day and the time needed to run 2 kilometers, you make a chart based on the data for a number of participants. Which variable do you put on the x-axis?

The independent or exploratory variable is put on the x-axis, and the dependent variable is put on the y-axis. The number of smoked cigarettes is the exploratory variable here: you want to know if (and how) this influences the condition of smokers.