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
3. Describing Data Numerically
Median
Problem 2.CR.15a
Textbook Question
Tail lengths (in feet) for a sample of American alligators are listed.
6.5 3.4 4.2 7.1 5.4 6.8 7.5 3.9 4.6
a. Find the mean, median, and mode of the tail lengths. Which best describes a typical American alligator tail length? Explain your reasoning.

1
Step 1: To find the mean, calculate the sum of all the tail lengths and divide by the total number of data points. Use the formula: , where is the sum of the data points and is the number of data points.
Step 2: To find the median, first arrange the tail lengths in ascending order: 3.4, 3.9, 4.2, 4.6, 5.4, 6.5, 6.8, 7.1, 7.5. Since there are 9 data points (an odd number), the median is the middle value in the ordered list.
Step 3: To find the mode, identify the value(s) that appear most frequently in the dataset. If no value repeats, then the dataset has no mode.
Step 4: Compare the mean, median, and mode to determine which best describes a typical American alligator tail length. Consider whether the data is symmetric or skewed, and whether outliers might affect the mean.
Step 5: Explain your reasoning by discussing the distribution of the data and how each measure of central tendency (mean, median, mode) reflects the dataset. For example, if the data is skewed, the median might be a better representation of a typical tail length than the mean.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Mean
The mean is the average of a set of numbers, calculated by summing all values and dividing by the count of values. It provides a central value that represents the data set, but can be influenced by extreme values (outliers). In the context of tail lengths, the mean gives a general idea of the average size of alligator tails.
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Median
The median is the middle value in a data set when the numbers are arranged in ascending order. If there is an even number of observations, the median is the average of the two middle numbers. It is a robust measure of central tendency that is less affected by outliers, making it useful for understanding typical values in skewed distributions.
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Mode
The mode is the value that appears most frequently in a data set. It is particularly useful for categorical data or when identifying the most common value in a numerical set. In the case of alligator tail lengths, the mode can indicate the most typical tail length, providing insight into common characteristics within the sample.
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