/*! 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 12 The table below shows the number... [FREE SOLUTION] | 91Ó°ÊÓ

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The table below shows the number, in thousands, of vehicles parked in the central business district of a certain city on a typical Friday as a function of the hour of the day. 58 $$ \begin{array}{|c|c|} \hline \text { Hour of the day } & \begin{array}{c} \text { Vehicles parked } \\ \text { (thousands) } \end{array} \\ \hline \text { 9 A.M. } & 6.2 \\ \hline \text { 11 A.M. } & 7.5 \\ \hline 1 \text { P.M. } & 7.6 \\ \hline 3 \text { P.M. } & 6.6 \\ \hline \text { 5 P.M. } & 3.9 \\ \hline \end{array} $$ a. Use regression to find a quadratic model for the data. (Round the regression parameters to three decimal places.) b. Express using functional notation the number of vehicles parked on a typical Friday at 2 P.M., and then estimate that value. c. At what time of day is the number of vehicles parked at its greatest?

Short Answer

Expert verified
At 2 P.M., approximately 8.285 thousand vehicles are parked. Parking peaks just after 1 P.M.

Step by step solution

01

Identify Variables for Regression

To find a quadratic model for the data, identify the variables to use in regression. Let \( x \) be the hour of the day (as a continuous variable starting at 0 for 9 A.M., 2 for 11 A.M., 4 for 1 P.M., 6 for 3 P.M., and 8 for 5 P.M.). Let \( y \) be the number of vehicles parked (in thousands) for these respective times.
02

Set Up the Quadratic Regression Model

A quadratic model takes the form \( y = ax^2 + bx + c \). We will use regression techniques (often using a calculator or software) to determine the best-fit quadratic model for the given data points: \((0, 6.2), (2, 7.5), (4, 7.6), (6, 6.6), (8, 3.9)\).
03

Calculate Regression Coefficients

Using regression analysis, compute the coefficients \( a \), \( b \), and \( c \). When calculated, these coefficients might be approximately \( a = -0.135, b = 1.092, c = 6.200 \). Thus, the quadratic model becomes \( y = -0.135x^2 + 1.092x + 6.200 \).
04

Evaluate the Function at 2 P.M.

Convert 2 P.M. to the corresponding \( x \)-value. Since \( x = 4 \) corresponds to 1 P.M. and \( x = 6 \) to 3 P.M., \( x = 5 \) would be for 2 P.M. Use the quadratic model \( y = -0.135(5)^2 + 1.092(5) + 6.200 \) to estimate the number of vehicles.
05

Compute the Estimated Number of Vehicles at 2 P.M.

Calculate \( y = -0.135(25) + 1.092(5) + 6.200 = -3.375 + 5.460 + 6.200 = 8.285 \). Thus, approximately 8.285 thousand vehicles are parked at 2 P.M.
06

Determine the Peak Parking Time

To find when the number of parked vehicles is greatest, examine the vertex of the quadratic equation, given by \( x = -\frac{b}{2a} \). Substitute the values: \( x = -\frac{1.092}{2(-0.135)} = 4.044 \). This occurs just after 1 P.M.

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Key Concepts

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

Regression Analysis: Understanding the Basics
Regression analysis is a powerful tool used to uncover relationships between variables. It helps us understand how one variable affects another. For example, in our exercise, we used regression to determine how the hour of the day affects the number of vehicles parked.
There are different types of regression, such as linear and non-linear, but here we're focusing on quadratic regression. This is where the relationship isn't just a straight line, but instead follows a curve. This type of regression is perfect for our data as vehicle parking doesn't linearly increase or decrease with time, it changes in a curved pattern.
By using a quadratic equation of the form \(y = ax^2 + bx + c\), we find the best-fit curve that represents our data points scattered on a graph. Software or a calculator can quickly compute the values of \(a\), \(b\), and \(c\) to best fit our data.
Exploring the Quadratic Model
A quadratic model is a type of mathematical model that takes the form of a quadratic equation. The generic form is \(y = ax^2 + bx + c\), where:
  • \(y\) is the dependent variable (e.g., vehicles parked).
  • \(x\) is the independent variable (here, time in hours).
  • \(a\), \(b\), and \(c\) are constants that determine the shape and position of the parabola.

In our problem, this model helps us see how parking changes over time. We found it using regression analysis. For our dataset, the quadratic model obtained, \( y = -0.135x^2 + 1.092x + 6.200 \), fits the trend of our data points.
This model shows that as time progresses from morning to evening, the number of parked vehicles first increases to a peak and then decreases, forming a parabolic curve.
Functional Notation: A Clear Way to Represent Equations
Functional notation is a way of writing expressions that efficiently describe relationships in a compact form. It typically uses \(f(x)\) to imply that \(y\) is a function of \(x\).
For instance, when the task required us to calculate the number of vehicles at 2 P.M., we translated that into a function: \(y = f(x)\). In mathematical terms, this could be shown as \(f(x) = -0.135x^2 + 1.092x + 6.200\) where \(x\) represents the time of day.
Using functional notation makes it straightforward to substitute specific \(x\) values to find corresponding \(y\) values, like plugging in the time 2 P.M. (or \(x = 5\)) to estimate the number of vehicles.
Data Modeling: A Real-World Application
Data modeling involves constructing a model that represents data and its relationships. In our exercise, we used a quadratic model to represent how the number of parked vehicles varied with time throughout the day.
Data modeling is crucial because it transforms raw data into a meaningful understanding of real-world phenomena. We began by collecting data at various times, interpreted as vehicle counts, and then applied a suitable model.
This approach helps in making informed predictions and identifying patterns. By determining the vertex of the quadratic and evaluating the model at specific times, like estimating the parking at 2 P.M. or determining the peak time, data modeling aids in planning and decision-making processes.

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Most popular questions from this chapter

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