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Voting and income A logistic regression model describes how the probability of voting for the Republican candidate in a presidential election depends on \(x,\) the voter's total family income (in thousands of dollars) in the previous year. The prediction equation for a particular sample is $$ \hat{p}=\frac{e^{-1.00+\operatorname{an} 2 x}}{1+e^{-1.00+0.02 x}} $$ Find the estimated probability of voting for the Republican candidate when (a) income \(=\$ 10,000\), (b) income \(=\$ 100,000 .\) Describe how the probability seems to depend on income.

Short Answer

Expert verified
The estimated probabilities are approximately 0.31 for $10,000 income and 0.73 for $100,000 income. Income increases the probability of voting Republican.

Step by step solution

01

Understanding the Logistic Regression Equation

The logistic regression model provided is \[ \hat{p} = \frac{e^{-1.00 + 0.02x}}{1 + e^{-1.00 + 0.02x}} \]where \( \hat{p} \) is the predicted probability of voting for the Republican candidate and \( x \) is the income in thousands of dollars. We will substitute different income values to find the predicted probability.
02

Convert Income to Thousands of Dollars

For the two income scenarios given, first convert the annual income from dollars to thousands of dollars:- For income \( = \\(10,000 \), then \( x = 10 \).- For income \( = \\)100,000 \), then \( x = 100 \).
03

Calculate Probability for Income = $10,000

Substitute \( x = 10 \) into the equation:\[ \hat{p} = \frac{e^{-1.00 + 0.02 \times 10}}{1 + e^{-1.00 + 0.02 \times 10}} = \frac{e^{-1.00 + 0.2}}{1 + e^{-1.00 + 0.2}} = \frac{e^{-0.8}}{1 + e^{-0.8}} \]Calculate \( e^{-0.8} \) using a calculator, which is approximately 0.4493:\[ \hat{p} = \frac{0.4493}{1 + 0.4493} \approx \frac{0.4493}{1.4493} \approx 0.3102 \] So, the estimated probability is approximately 0.31.
04

Calculate Probability for Income = $100,000

Now substitute \( x = 100 \) into the equation:\[ \hat{p} = \frac{e^{-1.00 + 0.02 \times 100}}{1 + e^{-1.00 + 0.02 \times 100}} = \frac{e^{-1.00 + 2}}{1 + e^{-1.00 + 2}} = \frac{e^{1.00}}{1 + e^{1.00}} \]Calculate \( e^{1.00} \) using a calculator, which is approximately 2.7183:\[ \hat{p} = \frac{2.7183}{1 + 2.7183} \approx \frac{2.7183}{3.7183} \approx 0.7316 \]So, the estimated probability is approximately 0.73.
05

Analyzing Probability Dependence on Income

From these computations, when the income increases from $10,000 to $100,000, the probability of voting for the Republican candidate increases significantly, from about 0.31 to 0.73. This suggests that higher income is associated with an increased probability of voting for the Republican candidate.

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Key Concepts

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

Voting Behavior Analysis
Voting behavior analysis is a fascinating field that combines statistics and social science to understand what motivates individuals to vote for certain candidates or parties. In this exercise, we explored how income can influence voting behavior in the context of a presidential election. Logistic regression, a type of statistical model, is commonly used to predict voting behavior based on certain predictors or factors, such as income. By using this model, researchers can estimate the probability of voters choosing a particular candidate. This is particularly useful in political strategy campaigns, as it helps identify target demographics most likely to support a candidate based on various variables.
In the presented exercise, the logistic regression equation is used to predict the likelihood of voting for a Republican candidate based on family income. By analyzing the model's results, we not only estimate probabilities but also gain insights into broader social trends, reflecting how socioeconomic status might influence political decisions. Understanding these underlying dynamics is crucial for developing more targeted and effective political campaigns.
Income Influence on Voting
The relationship between income and political preferences, such as the probability of voting for a Republican candidate, can be quite revealing. Income is a significant factor influencing voting choices, and can often indicate broader socioeconomic trends. The logistic regression model in our exercise shows that as family income increases, the probability of voting for the Republican candidate also increases.
Suppose we consider an income of $10,000, resulting in a candidate voting probability of approximately 0.31. Conversely, at an income of $100,000, this probability rises to about 0.73. These data points illustrate a clear pattern: higher income is associated with a higher likelihood of voting Republican.
  • This trend is interpreted to result from a range of political, economic, and personal values that might appeal more to higher-income individuals.
  • While this pattern aligns with common hypotheses in political science, it is important to acknowledge that individual decisions can be affected by numerous other factors.
The analysis emphasizes the role income plays in shaping voting behavior, offering critical insights for political analysts and campaign strategists alike.
Probability Calculation in Statistics
Probability calculation is a fundamental concept in statistics, allowing us to quantify uncertainties and make informed predictions. In logistics regression, probabilities are calculated using specific equations to model the likelihood of different outcomes.
In the exercise, the probability of a voter supporting a Republican candidate is calculated using the formula:
  • \[ \hat{p} = \frac{e^{-1.00 + 0.02x}}{1 + e^{-1.00 + 0.02x}} \] where \( \hat{p} \) represents the predicted probability, and \( x \) is the income in thousands of dollars.
Step-by-step probability calculation includes substituting income values into this equation, converting the income values into thousands of dollars, and computing the result.
For example, the calculation for an income of \(10,000 equates to a probability of approximately 0.31, while an income of \)100,000 yields a probability of around 0.73. These calculations help in interpreting the model's predictions and providing tangible expressions of abstract statistical predictions.
This rigorous approach to probability calculation ensures that results are both interpretable and actionable, providing a solid foundation for making data-driven decisions in various fields, beyond just voting behavior analysis.

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Most popular questions from this chapter

Predicting weight Let's use multiple regression to predict total body weight (TBW, in pounds) using data from a study of female college athletes. Possible predictors are \(\mathrm{HGT}=\) height (in inches), \(\% \mathrm{BF}=\) percent body fat, and age. The display shows the correlation matrix for these variables. a. Which explanatory variable gives by itself the best predictions of weight? Explain. b. With height as the sole predictor, \(\hat{y}=-106+3.65\) (HGT) and \(r^{2}=0.55\). If you add \%BF as a predictor, you know that \(R^{2}\) will be at least \(0.55 .\) Explain why. c. When you add \% body fat to the model, \(\hat{y}=-121+\) \(3.50(\mathrm{HGT})+1.35(\% \mathrm{BF})\) and \(R^{2}=0.66 .\) When you add age to the model, \(\hat{y}=-97.7+3.43(\mathrm{HGT})+\) \(1.36(\% \mathrm{BF})-0.960(\mathrm{AGE})\) and \(R^{2}=0.67\). Once you know height and \% body fat, does age seem to help you in predicting weight? Explain, based on comparing the \(R^{2}\) values.

Hall of Fame induction Baseball's highest honor is election to the Hall of Fame. The history of the election process, however, has been filled with controversy and accusations of favoritism. Most recently, there is also the discussion about players who used performance enhancement drugs. The Hall of Fame has failed to define what the criteria for entry should be. Several statistical models have attempted to describe the probability of a player being offered entry into the Hall of Fame. How does hitting 400 or 500 home runs affect a player's chances of being enshrined? What about having a 300 average or \(1500 \mathrm{RBI} ?\) One factor, the number of home runs, is examined by using logistic regression as the probability of being elected: $$ P(\mathrm{HOF})=\frac{e^{-6.7+0.0175 \mathrm{HR}}}{1+e^{-6.7+0.0175 \mathrm{HR}}} $$ a. Compare the probability of election for two players who are 10 home runs apart - say, 369 home runs versus 359 home runs. b. Compare the probability of election for a player with 475 home runs versus the probability for a player with 465 home runs. (These happen to be the figures for Willie Stargell and Dave Winficld.)

Predicting weight For a study of female college athletes, the prediction equation relating \(y=\) total body weight (in pounds) to \(x_{1}=\) height (in inches) and \(x_{2}=\) percent body fat is \(\hat{y}=-121+3.50 x_{1}+1.35 x_{2}\) a. Find the predicted total body weight for a female athlete at the mean values of 66 and 18 for \(x_{1}\) and \(x_{2}\). b. An athlete with \(x_{1}=66\) and \(x_{2}=18\) has actual weight \(y=115\) pounds. Find the residual and interpret it.

Controlling has an effect The slope of \(x_{1}\) is not the same for multiple linear regression of \(y\) on \(x_{1}\) and \(x_{2}\) as compared to simple linear regression of \(y\) on \(x_{1},\) where \(x_{1}\) is the only predictor. Explain why you would expect this to be true. Does the statement change when \(x_{1}\) and \(x_{2}\) are uncorrelated?

Does study help GPA? For the Georgia Student Survey file on the book's website, the prediction equation relating \(y=\) college \(\mathrm{GPA}\) to \(x_{1}=\) high school GPA and \(x_{2}=\) study time (hours per day), is \(\hat{y}=1.13+\) \(0.643 x_{1}+0.0078 x_{2}\) a. Find the predicted college GPA of a student who has a high school GPA of 3.5 and who studies three hours a day. b. For students with fixed study time, what is the change in predicted college GPA when high school GPA increases from 3.0 to \(4.0 ?\)

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