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91Ó°ÊÓ

For each of the following pairs of variables, indicate whether you would expect a positive correlation, a negative correlation, or a correlation close to \(0 .\) Explain your choice. a. Interest rate and number of loan applications b. Height and \(\mathrm{IQ}\) c. Height and shoe size d. Minimum daily temperature and cooling cost

Short Answer

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a. Negative correlation - High interest rates discourage loan applications, while low interest rates encourage them. b. Correlation close to 0 - Height and IQ are generally unrelated variables. c. Positive correlation - Taller people generally have larger feet and hence larger shoe sizes. d. Negative correlation - On cooler days, demand for cooling is lower, reducing cooling costs, while on warmer days, demand increases, raising cooling costs.

Step by step solution

01

a. Interest rate and number of loan applications

For this pair of variables, we would expect a negative correlation. When interest rates are high, borrowing becomes more expensive, and people are less likely to apply for loans. Conversely, when interest rates are low, borrowing is cheaper, and people are more motivated to apply for loans.
02

b. Height and IQ

For this pair of variables, we would expect a correlation close to 0. Height and IQ are unrelated variables, so there should be no strong positive or negative correlation between them. It's important to note that exceptions might exist, but generally, one's height does not influence their intelligence.
03

c. Height and shoe size

For this pair of variables, we would expect a positive correlation. Taller people generally have larger feet and thus require larger shoe sizes. While this may not be true in every case, overall a positive trend can be observed between height and shoe size.
04

d. Minimum daily temperature and cooling cost

For this pair of variables, we would expect a negative correlation. On cooler days, the minimum daily temperature is lower, and there is less need for cooling; as a result, cooling costs would be lower. Conversely, on warmer days with higher minimum daily temperatures, the demand for cooling is higher, leading to increased cooling costs.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Negative Correlation
In statistics, a negative correlation describes a relationship between two variables in which one variable increases as the other decreases. This is an inverse relationship. Let's consider the example of interest rates and loan applications. When interest rates rise, borrowing becomes more expensive, causing the number of loan applications to drop. Conversely, when interest rates decrease, borrowing is cheaper, potentially leading to more loan applications. This inverse relationship is a classic example of negative correlation.
Negative correlations are useful in predictive analysis. They can help businesses anticipate changes and adjust strategies accordingly. For example, a company might prepare for a decrease in loan applications if they foresee an increase in interest rates. Understanding negative correlations allows decision-makers to make informed predictions and adapt to changes in the market. Remember, a perfect negative correlation is represented by -1 in linear regression models.
Positive Correlation
A positive correlation occurs when two variables increase or decrease in tandem. When one variable rises, the other follows suit, and when one falls, the other also diminishes. The relationship between height and shoe size illustrates positive correlation. Generally, as people get taller, their shoe size tends to get larger as well. This relationship is consistent enough to observe a positive trend.
Positive correlations are significant in understanding trends and patterns in data. They allow us to make predictions about one variable based on the behaviour of another. For example, retailers could use the positive correlation between height and shoe size to optimize their inventory, ensuring a suitable range of shoe sizes based on customer demographics. A perfect positive correlation is represented by a value of +1.
Variables Analysis
Analyzing variables is a critical step in understanding data relationships. Variables represent characteristics or phenomena that we are interested in studying or measuring. To analyze them, we often calculate correlations to understand their relationships, which can be positive, negative, or close to zero.
Consider height and IQ. Despite being measurable variables, they typically show a correlation close to zero, indicating no strong relationship between them. This analysis helps us confirm or debunk hypotheses regarding variables with actual data. In research and practical applications, understanding whether variables are related can improve decision-making and hypothesis testing.
When analyzing variables, it's essential to use appropriate statistical methods to test for correlation and measure the strength of relationships. Incorrect assumptions can lead to errors, so verifying relationships with statistical tools is paramount.
Statistical Relationships
Statistical relationships allow us to understand how different variables interact with each other. They form the basis of many predictive models and analytical frameworks. By examining statistical relationships, we can determine if changes in one variable might lead to changes in another.
For instance, consider the relationship between minimum daily temperature and cooling cost. On cooler days, the need for cooling drops, leading to reduced energy costs, which is a negative statistical relationship. Understanding these relationships helps in planning and resource management.
To analyze statistical relationships effectively, it’s important to gather accurate data and apply correct statistical techniques. This helps in building reliable models that predict outcomes based on identified relationships. Remember, statistical relationships are key to making informed predictions about future events.

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Most popular questions from this chapter

An auction house released a list of 25 recently sold paintings. The artist's name and the sale price of each painting appear on the list. Would the correlation coefficient be an appropriate way to summarize the relationship between artist and sale price? Why or why not?

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The paper "Noncognitive Predictors of Student Athletes' Academic Performance" (Journal of College Reading and Learning [2000]: e167) summarizes a study of 200 Division I athletes. It was reported that the correlation coefficient for college grade point average (GPA) and a measure of academic self-worth was \(r=0.48\). Also reported were the correlation coefficient for college GPA and high school GPA \((r=0.46)\) and the correlation coefficient for college GPA and a measure of tendency to procrastinate \((r=-0.36) .\) Write a few sentences summarizing what these correlation coefficients tell you about GPA for the 200 athletes in the sample.

Draw two scatterplots, one for which \(r=1\) and a second for which \(r=-1\).

In a study of the relationship between TV viewing and eating habits, a sample of 548 ethnically diverse students from Massachusetts was followed over a 19 -month period (Pediatrics [2003]: 1321-1326). For each additional hour of television viewed per day, the number of fruit and vegetable servings per day was found to decrease on average by 0.14 serving. a. For this study, what is the response variable? What is the predictor variable? b. Would the least squares regression line for predicting number of servings of fruits and vegetables using number of hours spent watching TV have a positive or negative slope? Justify your choice.

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