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A sample of 548 ethnically diverse students from Massachusetts were followed over a 19 -month period from 1995 and 1997 in a study of the relationship between TV viewing and eating habits (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 dependent variable? What is the predictor variable? b. Would the least-squares line for predicting number of servings of fruits and vegetables using number of hours spent watching TV as a predictor have a positive or negative slope? Explain.

Short Answer

Expert verified
a. The dependent variable here is the 'number of fruit and vegetable servings per day', and the predictor variable is the 'number of hours of television viewed per day'. b. The least-squares line would have a negative slope because according to the data, increased television viewing leads to a decrease in fruit and vegetable consumption.

Step by step solution

01

Identify the dependent variable

The dependent variable is what you measure in the experiment and what is affected during the experiment. In this case, what is being measured is the number of fruit and vegetable servings per day. So, the dependent variable is the 'number of fruit and vegetable servings per day'.
02

Identify the predictor variable

The predictor variable is a variable that is being manipulated in an experiment in order to impact the dependent variable. In this example, the predictor or independent variable is 'the number of hours of television viewed per day'.
03

Predict the slope of the least-squares line

According to the study, 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. This indicates a negative correlation between the hours of television viewed and the servings of fruits and vegetables consumed. Therefore, the least-squares line for predicting the number of servings of fruits and vegetables using the number of hours spent watching TV as a predictor would have a negative slope.

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Key Concepts

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

Statistical Analysis
Statistical analysis is an essential element in interpreting data and making decisions based on that data. It covers a range of techniques and processes that enable researchers to summarize, interpret, and make predictions from various data sets. In the study of the relationship between TV viewing and eating habits, statistical analysis is used to explore the data collected from the ethnically diverse students. Specifically, the analysis here aims to quantify the change in the average number of fruit and vegetable servings as the number of hours of television viewing increases.
Through this process, researchers can assess patterns, relationships, and trends, which are crucial for understanding the dynamics between different variables. The value of statistical analysis becomes particularly evident when we can quantify exact figures, such as the decrease of 0.14 servings of fruits and vegetables for each additional hour of TV viewed, allowing for clearer and more precise insights into the studied phenomena.
Correlation
Correlation is a statistical measure that describes the extent to which two variables change together. It has a range from -1 to 1 where values closer to -1 indicate a strong negative correlation, values closer to 1 represent a strong positive correlation, and values around 0 suggest no correlation. In the context of the study, correlation is used to determine the relationship between the amount of television watched and the number of servings of fruits and vegetables consumed.
A negative correlation was identified, signifying that as one variable increases, the other decreases. Specifically, every extra hour of television correlates with a decrease of 0.14 servings in fruit and vegetable intake. This correlation is essential in understanding how one behavior may potentially impact dietary choices, and it provides a foundation for the formulation of public health recommendations or interventions.
Least-Squares Line
The least-squares line, also known as the line of best fit, is a straight line that best represents the data on a scatter plot. This line minimizes the sum of the squares of the vertical distances of the points from the line (the residuals). In the study, this line would be used to predict the number of servings of fruits and vegetables based on the number of hours of television viewed.
Given the negative correlation in the study, the least-squares line will have a negative slope, indicating that as the number of hours of TV watching increases, the predicted number of fruit and vegetable servings decreases. This line is a powerful tool in predicting future outcomes and can help elucidate the strength and direction of a relationship between variables.
Variable Manipulation
Variable manipulation involves altering one variable to determine if changes in it cause changes in another variable. This is a crucial aspect of experiments and studies intended to understand cause-and-effect relationships. In the described study, the predictor variable, which is the number of hours of television viewed per day, is manipulated to observe changes in the dependent variable, the number of fruit and vegetable servings consumed per day.
It's important to remember that observing changes does not necessarily establish causation. However, consistent patterns of variable manipulation followed by expected changes in the dependent variable can strengthen the argument for a causal effect. In this case, the study suggests that increased television viewing may be causing a decrease in fruit and vegetable servings among students.

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Most popular questions from this chapter

Cost-to-charge ratio (the percentage of the amount billed that represents the actual cost) for inpatient and outpatient services at 11 Oregon hospitals is shown in the following table (Oregon Department of Health Services, 2002). A scatterplot of the data is also shown. $$ \begin{array}{ccc} \hline \text { Hospital } & \begin{array}{l} \text { Outpatient } \\ \text { Care } \end{array} & \begin{array}{l} \text { Inpatient } \\ \text { Care } \end{array} \\ \hline 1 & 62 & 80 \\ 2 & 66 & 76 \\ 3 & 63 & 75 \\ 4 & 51 & 62 \\ 5 & 75 & 100 \\ 6 & 65 & 88 \\ 7 & 56 & 64 \\ 8 & 45 & 50 \\ 9 & 48 & 54 \\ 10 & 71 & 83 \\ 11 & 54 & 100 \\ \hline \end{array} $$ The least-squares regression line with \(y=\) inpatient costto-charge ratio and \(x=\) outpatient cost-to-charge ratio is \(\hat{y}=-1.1+1.29 x\). a. Is the observation for Hospital 11 an influential observation? Justify your answer. b. Is the observation for Hospital 11 an outlier? Explain. c. Is the observation for Hospital 5 an influential observation? Justify your answer. d. Is the observation for Hospital 5 an outlier? Explain.

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