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Ch. 1 - Introduction to Statistics
Triola - Elementary Statistics 14th Edition
Triola14th EditionElementary StatisticsISBN: 9780137366446Not the one you use?Change textbook
Chapter 1, Problem 1.RE.4

Divorces and Margarine One study showed that there is a very high correlation between the divorce rate in Maine and per capita consumption of margarine in the United States. Can we conclude that either one of those two variables is the cause of the other?

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1
Understand the concept of correlation: Correlation measures the strength and direction of a linear relationship between two variables. A high correlation indicates a strong relationship, but it does not imply causation.
Identify the concept of causation: Causation implies that one event is the result of the occurrence of the other event; i.e., there is a cause-and-effect relationship between the two variables.
Consider the possibility of a spurious correlation: A spurious correlation occurs when two variables appear to be related due to the presence of a third variable or purely by chance, rather than a direct causal relationship.
Evaluate the context of the variables: In this case, the divorce rate in Maine and the per capita consumption of margarine in the United States are unlikely to have a direct causal relationship. Consider other factors that might influence both variables independently.
Conclude that correlation does not imply causation: Even with a high correlation, we cannot conclude that one variable causes the other without further evidence or analysis. Additional research would be needed to explore any potential causal relationships.

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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 change together. However, correlation does not imply causation, meaning that one variable directly affects the other. In the given question, a high correlation between divorce rates and margarine consumption does not mean one causes the other; they may be influenced by other factors or be coincidentally related.
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Spurious Correlation

A spurious correlation occurs when two variables appear to be related but are actually influenced by a third variable or are coincidentally correlated. In the case of divorce rates and margarine consumption, the correlation might be spurious, suggesting that the relationship is not due to direct causation but rather due to other underlying factors or random chance.
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Confounding Variables

Confounding variables are external factors that can affect the relationship between the studied variables, potentially leading to misleading conclusions. In the context of the question, there might be confounding variables affecting both divorce rates and margarine consumption, such as economic conditions or cultural trends, which could explain the observed correlation without implying causation.
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Related Practice
Textbook Question

Sampling For each of the following, identify the term that best describes the type of sample: systematic, convenience, stratified, cluster, or simple random sample.


a. As Lipitor pills are being manufactured, a quality control plan is to select every 500th pill and test it to confirm that it contains 80 mg of atorvastatin.

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Textbook Question

Paying for First Dates USA Today posted this question on the electronic version of its newspaper: “Should guys pay for the first date?” Of the 1148 subjects who decided to respond, 85% of them said “yes.”


b. Is the value of 85% a statistic or a parameter?

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Textbook Question

State Populations Currently, California has the largest population with 39,776,830 residents, and Wyoming has the smallest population with 573,520 residents.


e. If we randomly select two states and survey all of their adult residents, what type of sample is obtained? (random, systematic, convenience, stratified, cluster)

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Textbook Question

Paying for First Dates USA Today posted this question on the electronic version of its newspaper: “Should guys pay for the first date?” Of the 1148 subjects who decided to respond, 85% of them said “yes.”


a. What is wrong with this survey?

251
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Textbook Question

State Populations Currently, California has the largest population with 39,776,830 residents, and Wyoming has the smallest population with 573,520 residents.


d. If we randomly select 50 full-time workers in each of the 50 states, what type of sample is obtained? (random, systematic, convenience, stratified, cluster)

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Textbook Question

Sampling For each of the following, identify the term that best describes the type of sample: systematic, convenience, stratified, cluster, or simple random sample.


b. To test for a gender difference in the way that men and women make online purchases, Gallup surveys 500 randomly selected men and 500 randomly selected women.

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