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Ch. 1 - Introduction to Statistics
Triola - Elementary Statistics 14th Edition
Triola14th EditionElementary StatisticsISBN: 9780137366446Not the one you use?Change textbook
All textbooksTriola 14th EditionCh. 1 - Introduction to StatisticsProblem 1.1.28
Chapter 1, Problem 1.1.28

In Exercises 25–28, refer to the data in the table below. The entries are for five different years, and they consist of weights (metric tons) of lemons imported from Mexico and U.S. car crash fatality rates per 100,000 population [based on data from “The Trouble with QSAR (or How I Learned to Stop Worrying and Embrace Fallacy)” by Stephen Johnson, Journal of Chemical Information and Modeling, Vol. 48, No. 1].
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Conclusion If we were to use the sample data and conclude that there is a correlation or association between lemon imports and crash fatality rates, does it follow that lemon imports are the cause of fatal crashes?

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Step 1: Understand the problem. The question is asking whether a correlation or association between two variables (lemon imports and car crash fatality rates) implies causation. This is a common statistical concept where correlation does not necessarily mean causation.
Step 2: Define the key terms. Correlation refers to a statistical relationship between two variables, which can be positive, negative, or zero. Causation, on the other hand, implies that one variable directly affects the other. It is important to distinguish between these two concepts.
Step 3: Analyze the data. Look at the data provided in the table. Calculate the correlation coefficient (r) to determine the strength and direction of the relationship between lemon imports and car crash fatality rates. Use the formula for Pearson's correlation coefficient: r=∑(x-x¯)(y-y¯)(∑(x-x¯))2(∑(y-y¯))2. Here, x and y represent the two variables, and x̄ and ȳ are their respective means.
Step 4: Interpret the correlation coefficient. If the correlation coefficient is close to 1 or -1, it indicates a strong relationship. If it is close to 0, it indicates a weak or no relationship. However, even if a strong correlation exists, it does not imply causation. Other factors, such as confounding variables, could be influencing the relationship.
Step 5: Draw a conclusion. Based on the statistical analysis and the concept of correlation versus causation, explain that even if a correlation is found between lemon imports and car crash fatality rates, it does not mean that lemon imports cause fatal crashes. This could be an example of a spurious correlation, where two variables appear to be related but are not causally connected.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Correlation vs. Causation

Correlation refers to a statistical relationship between two variables, indicating that they tend to move together. However, this does not imply that one variable causes the other. Understanding this distinction is crucial, as it helps prevent erroneous conclusions about the nature of the relationship, especially in observational data where confounding factors may be present.
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Confounding Variables

Confounding variables are external factors that may influence both the independent and dependent variables, potentially leading to misleading interpretations of data. In the context of the question, other factors could affect both lemon imports and car crash fatality rates, making it essential to identify and control for these variables to draw valid conclusions.
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Statistical Significance

Statistical significance assesses whether the observed relationship in data is likely due to chance. A statistically significant result suggests that the correlation observed is unlikely to have occurred randomly. However, it is important to remember that statistical significance does not imply practical significance or causation, which must be evaluated through further analysis.
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Related Practice
Textbook Question

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b. Is the value of 3.7% a statistic or parameter?

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Textbook Question

In Exercises 13–20, determine whether the data are from a discrete or continuous data set.

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Textbook Question

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Textbook Question

In Exercises 9–12, determine whether the sampling method appears to be sound or is flawed.


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Textbook Question

In Exercises 21–24, refer to the sample of body temperatures (degrees Fahrenheit) in the table below. (The body temperatures are from Data Set 5 in Appendix B.)

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Conclusion Given the body temperatures in the table, what issue can be addressed by conducting a statistical analysis of the data?

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Textbook Question

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