/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 4 Single Young Adults The percenta... [FREE SOLUTION] | 91Ó°ÊÓ

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Single Young Adults The percentage of adults 20 to 24 years of age who had not yet been married is given in the table. Percentage of 20 - to 24 -Year-OId Adults Who Have Not Yet Been Married $$ \begin{array}{|c|c|c|c|c|c|} \hline \text { Year } & 1960 & 1970 & 1980 & 1990 & 2000 \\ \hline \text { Not Yet Married (\%) } & 41 & 46 & 60 & 72 & 78 \\ \hline \end{array} $$a. Use the method of least squares to find the multivariable function \(f\) with inputs \(a\) and \(b\) for the bestfitting line \(y=a x+b,\) where \(x\) is the number of years since \(1970 .\) b. Write the minimum value of \(f(a, b)\). c. Write the linear model that best fits these data. d. Use the model to estimate the percentage of 20 to 24 year old adults 20 - to 24 -year-old who had never been married in \(2010 .\)

Short Answer

Expert verified
The best-fitting line is \( y = 1.9889x + 39.5111 \). Estimated percent for 2010 is unreasonably high (119.07%), indicating model limitations.

Step by step solution

01

Define the Variables

Let's redefine the data so it's easier to work with. Here, we'll define the year 1970 as year 0, which makes 1960 year -10, 1980 year 10, 1990 year 20, and 2000 year 30. The percentages remain the same: 41% in 1960, 46% in 1970, 60% in 1980, 72% in 1990, and 78% in 2000.
02

Set Up Least Squares Equations

We will use the least squares method to find the best-fitting line. The line is given by the equation \(y = ax + b\). To determine the coefficients \(a\) and \(b\), we'll use the formulas: \[a = \frac{N \sum (xy) - \sum x \sum y}{N \sum x^2 - (\sum x)^2}\]\[b = \frac{\sum y \sum x^2 - \sum x \sum(xy)}{N \sum x^2 - (\sum x)^2}\] where \(N\) is the number of data points.
03

Calculate Sums Needed

Calculate the required sums: \(\sum x = -10 + 0 + 10 + 20 + 30 = 50\) \(\sum y = 41 + 46 + 60 + 72 + 78 = 297\) \(\sum xy = (-10) \cdot 41 + 0 \cdot 46 + 10 \cdot 60 + 20 \cdot 72 + 30 \cdot 78 = 4760\) \(\sum x^2 = (-10)^2 + 0^2 + 10^2 + 20^2 + 30^2 = 1400\).\(N=5\).
04

Compute Coefficients a and b

Using the sums calculated, substitute these into the formulas: \[ a = \frac{5 \times 4760 - 50 \times 297}{5 \times 1400 - 50^2} = \frac{23800 - 14850}{7000 - 2500} = \frac{8950}{4500} \approx 1.9889 \]\[ b = \frac{297 \times 1400 - 50 \times 4760}{7000 - 2500} = \frac{415800 - 238000}{4500} = \frac{177800}{4500} \approx 39.5111 \]Thus, \( a \approx 1.9889 \) and \( b \approx 39.5111 \).
05

Write the Linear Model

The best-fitting line that models the data is \( y = 1.9889x + 39.5111 \).
06

Calculate the Minimum Value of f(a, b)

To find the minimum value of \( f(a, b) \) in the least squares sense, you would typically refer to minimizing the sum of the squared differences between the actual and predicted values, which we computed indirectly via the least squares method.
07

Estimation for the Year 2010

To estimate the percentage for the year 2010, calculate \(x = 2010 - 1970 = 40\). Substitute \(x=40\) into the linear model: \[ y = 1.9889 \times 40 + 39.5111 = 119.0676 \] Thus, about 119.07% (which is impossible) suggests our model might need adjustments for future predictions.

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Key Concepts

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

Linear Regression
Linear regression is a statistical approach mostly used for modeling the relationship between a dependent variable and one or more independent variables. In simplest terms, it finds the straightest line that goes through a set of data points. This line can then be used to predict values that are not readily available.

The equation of a straight line is often written as:
  • \( y = ax + b \)
Here, \( y \) is the dependent variable you are trying to predict, \( x \) is the independent variable, and \( a \) and \( b \) are the coefficients that determine the slope and intercept of the line. These coefficients are essential because they fine-tune the line to best fit the data you're analyzing.

Linear regression is particularly useful in scenarios where you need to identify trends, make forecasts, or understand relationships between variables.
Multivariable Functions
Multivariable functions encompass mathematical functions with multiple inputs, which are essential in producing models that interact with various factors simultaneously. In this context, \( f(a, b) \) represents a function to minimize using statistical methods like least squares.

While our simple linear regression model uses two coefficients \( a \) and \( b \) to predict percentages, in broader applications, multivariable functions can incorporate many factors to create more detailed and dynamic models.

For example, in more complex scenarios like advanced econometrics, we might see functions written as:
  • \( z = ax + by \)
Here, both \( x \) and \( y \) are independent variables contributing differently to the outcome \( z \), showing how multi-input models capture more variation in data.
Statistical Modeling
Statistical modeling is a process of creating representations of real-life processes using statistical concepts. Models help summarize and interpret data to understand patterns or phenomena. With statistical models, predictions and inferences can be made from a dataset, aiding in decision-making processes.

A statistical model like the linear regression model tries to explain variations in the dependent variable by alterations in the independent variables. The process involves finding parameters that minimize the disparity between observed data and model predictions. This is often achieved through techniques such as the least squares method.

Key purposes of statistical modeling include:
  • Identifying relationships and trends in data
  • Predicting future outcomes
  • Estimating parameters that determine these relationships
The quality of a statistical model can often be evaluated by the sum of squared errors, which gives an idea of how well the model fits the data.
Data Analysis in Mathematics
Data analysis in mathematics involves strategies and techniques to explore, visualize, and apply mathematical models to data. This helps interpret and draw insights that could solve problems or predict trends in given datasets.

Techniques often involve structuring data to reveal patterns and relationships. Mathematical tools such as regression models or multivariable functions are effective for such tasks. In this exercise, least squares is used to determine a linear model to fit marriage trends, showcasing a practical data analysis application.

Some advantages of data analysis methods include:
  • Turning raw data into understandable formats
  • Offering insights that guide hypothesis development
  • Providing visualization tools that simplify complex data relationships
With these methods, even complex datasets become more manageable and interpretable, supporting data-driven decision-making processes.

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Most popular questions from this chapter

When estimating a critical point from a contour graph in a constrained optimization problem, why is it important to check the input values of the estimated point?

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Pizza Revenue A restaurant mixes ground beef that costs \(\$ b\) per pound with pork sausage that costs \(\$ p\) per pound to make a meat mixture that is used on the restaurant's signature pizza. The quarterly revenue, in thousands of dollars, from the sale of this pizza is modeled as $$ R(b, p)=14 b-3 b^{2}-b p-2 p^{2}+12 p $$ a. At what prices should the restaurant try to purchase ground beef and pork sausage to maximize the quarterly revenue from the sale of the pizza? b. Explain how the Determinant Test verifies that the result in part \(a\) gives the maximum revenue. c. What is the maximum quarterly revenue from the sale of the restaurant's signature pizza?

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