Table of contents
- 1. Intro to Stats and Collecting Data55m
- 2. Describing Data with Tables and Graphs1h 55m
- 3. Describing Data Numerically1h 45m
- 4. Probability2h 16m
- 5. Binomial Distribution & Discrete Random Variables2h 33m
- 6. Normal Distribution and Continuous Random Variables1h 38m
- 7. Sampling Distributions & Confidence Intervals: Mean1h 3m
- 8. Sampling Distributions & Confidence Intervals: Proportion1h 12m
- 9. Hypothesis Testing for One Sample1h 1m
- 10. Hypothesis Testing for Two Samples2h 8m
- 11. Correlation48m
- 12. Regression1h 4m
- 13. Chi-Square Tests & Goodness of Fit1h 20m
- 14. ANOVA1h 0m
2. Describing Data with Tables and Graphs
Frequency Distributions
Problem 2.1.8
Textbook Question
In Exercises 5–8, identify the class width, class midpoints, and class boundaries for the given frequency distribution. Also identify the number of individuals included in the summary. The frequency distributions are based on real data from Appendix B.
8. 

1
Step 1: Identify the class width. The class width is calculated by subtracting the lower boundary of one class from the lower boundary of the next class. For example, subtract 100 from 200 to get the class width: 200 - 100 = 100.
Step 2: Calculate the class midpoints. The midpoint of each class is found by averaging the lower and upper boundaries of the class. For example, for the first class (100–199), the midpoint is (100 + 199) / 2 = 149.5. Repeat this for all classes.
Step 3: Determine the class boundaries. The boundaries are calculated by subtracting 0.5 from the lower limit and adding 0.5 to the upper limit of each class. For example, for the first class (100–199), the boundaries are 99.5 and 199.5. Repeat this for all classes.
Step 4: Sum the frequencies to find the total number of individuals included in the summary. Add all the frequencies together: 25 + 92 + 28 + 0 + 2.
Step 5: Verify the calculations and ensure all values (class width, midpoints, boundaries, and total frequency) are consistent with the given data.

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