Data Foundations Checkpoint
A free Statistics and Data Analysis lesson from the “Data Foundations” unit, with a worked example and practice problems including step-by-step solutions.
This checkpoint reviews data types, displays, center, spread, outliers, and distribution comparisons before moving into two-variable data.
What you'll learn
- Review the major skills from this part of the course
- Choose an appropriate statistical method
- Explain results in context
Worked example
Problem. A bar chart has 10 votes for A out of 27 total votes. About what percent chose A? Enter the nearest whole percent.
- Worked Example: First identify exactly what the question is asking: A bar chart has 10 votes for A out of 27 total votes. About what percent chose A? Enter the nearest whole percent.
- For percents, convert the percent to a decimal or fraction and connect it to the base amount in the problem.
- Relative frequency is count divided by total.
- 10 / 27 is about 37%.
Answer: 37
Practice problems
1. Review case A: A bar chart has 10 votes for A out of 27 total votes. About what percent chose A? Enter the nearest whole percent.
Show solution
- Checkpoint Review: First identify exactly what the question is asking: A bar chart has 10 votes for A out of 27 total votes. About what percent chose A? Enter the nearest whole percent.
- For percents, convert the percent to a decimal or fraction and connect it to the base amount in the problem.
- Relative frequency is count divided by total.
- 10 / 27 is about 37%.
- Check the result by substituting or estimating: the response should match 37 and make sense in the original problem.
Answer: 37
2. Review case B: Which display is best for comparing counts across categories?
Choices: Residual plot · Bar chart · Histogram · Box plot
Show solution
- Checkpoint Review: First identify exactly what the question is asking: Which display is best for comparing counts across categories?
- Compare each answer choice with the calculation or rule, and eliminate choices that do not satisfy the condition.
- A bar chart compares category counts.
- Histograms and box plots are for quantitative distributions.
- Verify the selected choice by checking that it satisfies the original prompt and that the other choices fail the same test.
Answer: Bar chart
3. Review case C: A histogram is used mainly to show:
Choices: the shape of quantitative data · the exact value of a population parameter · the cause of an association · the treatment in an experiment
Show solution
- Checkpoint Review: First identify exactly what the question is asking: A histogram is used mainly to show:
- Compare each answer choice with the calculation or rule, and eliminate choices that do not satisfy the condition.
- Histograms group quantitative values into intervals.
- That reveals distribution shape.
- Verify the selected choice by checking that it satisfies the original prompt and that the other choices fail the same test.
Answer: the shape of quantitative data
4. Review case D: A box plot has Q1 = 12, median = 14, and Q3 = 16. Find the IQR.
Show solution
- Checkpoint Review: First identify exactly what the question is asking: A box plot has Q1 = 12, median = 14, and Q3 = 16. Find the IQR.
- For data questions, identify what each statistic measures before calculating so the result matches the question.
- IQR measures the spread of the middle half.
- 16 - 12 = 4.
- Check the result by substituting or estimating: the response should match 4 and make sense in the original problem.
Answer: 4
5. Review case E: Find the median of 13, 4, 16, 7, 10.
Show solution
- Checkpoint Review: First identify exactly what the question is asking: Find the median of 13, 4, 16, 7, 10.
- For data questions, identify what each statistic measures before calculating so the result matches the question.
- Order the data from least to greatest.
- The middle value is 10.
- Check the result by substituting or estimating: the response should match 10 and make sense in the original problem.
Answer: 10
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