Math Problem Statement

The following table shows the value of a car over time that was purchased for 18200 dollars, where x is years and y is the value of the car in dollars. Write an exponential regression equation for this set of data, rounding all coefficients to the nearest hundredth. Years (x) | Value $ (y) 0 | 18200 1 | 14824 2 | 13651 3 | 11593 4 | 10590 Use y = a(b)^x as your regression equation.

Solution

To solve this problem, we need to compute an exponential regression model in the form:

y=a(b)xy = a(b)^x

Steps:

  1. Determine aa:

    • aa represents the initial value of yy when x=0x = 0. From the table, a=18200a = 18200.
  2. Determine bb:

    • bb is the growth (or decay) factor and can be calculated as: b=yny0nb = \sqrt[n]{\frac{y_n}{y_0}} Here, y0y_0 is the initial value (18200), and yny_n is the value at x=nx = n. We will use several values to calculate bb.
  3. Calculate the correlation coefficient rr:

    • This measures how well the exponential model fits the data.

Let me calculate these values for you.Here are the results for the exponential regression:

  1. a=18200a = 18200 (initial value when x=0x = 0).
  2. b=0.88b = 0.88 (decay factor, rounded to the nearest hundredth).
  3. r=0.99r = -0.99 (correlation coefficient, indicating a strong negative relationship).

Regression equation:

y=18200(0.88)xy = 18200(0.88)^x

Let me know if you need detailed explanations for any step or additional analysis!

Related Questions:

  1. How does the correlation coefficient rr affect the interpretation of the model's fit?
  2. Can you calculate the expected value of the car after 5 years using the regression equation?
  3. How would the regression change if the decay factor bb were larger than 1?
  4. Why is exponential regression appropriate for this data instead of linear regression?
  5. How can we verify the model's accuracy with residuals?

Tip:

In exponential models, the decay factor bb gives a direct measure of the rate of decrease (or increase) per unit of xx.

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Math Problem Analysis

Mathematical Concepts

Algebra
Exponential Decay
Regression Analysis

Formulas

y = a(b)^x
b = (y_n / y_0)^(1/n)
Correlation coefficient (r)

Theorems

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Suitable Grade Level

Grades 9-12