Math Problem Statement

The table below gives the list price and the number of bids received for five randomly selected items sold through online auctions. Using this data, consider the equation of the regression line, yˆ=b0+b1x, for predicting the number of bids an item will receive based on the list price. Keep in mind, the correlation coefficient may or may not be statistically significant for the data given. Remember, in practice, it would not be appropriate to use the regression line to make a prediction if the correlation coefficient is not statistically significant.

Price in Dollars 23 24 32 37 49 Number of Bids 1 2 6 9 10

Solution

To find the equation of the regression line y^=b0+b1x\hat{y} = b_0 + b_1x for predicting the number of bids (y^\hat{y}) based on the list price (xx), we need to calculate the slope (b1b_1) and the y-intercept (b0b_0) of the regression line. Here are the steps involved:

Step 1: Calculate the Means

Calculate the mean of the list prices (x\overline{x}) and the mean of the number of bids (y\overline{y}).

x=23+24+32+37+495\overline{x} = \frac{23 + 24 + 32 + 37 + 49}{5}

y=1+2+6+9+105\overline{y} = \frac{1 + 2 + 6 + 9 + 10}{5}

Step 2: Calculate the Slope (b1b_1)

The slope b1b_1 is calculated using the formula:

b1=(xix)(yiy)(xix)2b_1 = \frac{\sum (x_i - \overline{x})(y_i - \overline{y})}{\sum (x_i - \overline{x})^2}

Step 3: Calculate the Y-intercept (b0b_0)

The y-intercept b0b_0 is calculated using the formula:

b0=yb1xb_0 = \overline{y} - b_1\overline{x}

Step 4: Compute the Correlation Coefficient (Optional)

To determine if the regression line is statistically significant, you may calculate the correlation coefficient rr using:

[ r = \frac{n\sum(x_i y_i) - \sum x_i \sum y_i}{\sqrt{[n\sum x_i^2 - (\sum x_i)^2][n\sum y_i^2 - (\sum y_i)^2]}} ]

Let's go through these calculations step by step.

Step 1: Calculate the Means

x=23+24+32+37+495=1655=33\overline{x} = \frac{23 + 24 + 32 + 37 + 49}{5} = \frac{165}{5} = 33

y=1+2+6+9+105=285=5.6\overline{y} = \frac{1 + 2 + 6 + 9 + 10}{5} = \frac{28}{5} = 5.6

Step 2: Calculate the Slope (b1b_1)

First, calculate (xix)(x_i - \overline{x}) and (yiy)(y_i - \overline{y}) for each data point:

[ (x_i - \overline{x}) = [23-33, 24-33, 32-33, 37-33, 49-33] = [-10, -9, -1, 4, 16] ]

[ (y_i - \overline{y}) = [1-5.6, 2-5.6, 6-5.6, 9-5.6, 10-5.6] = [-4.6, -3.6, 0.4, 3.4, 4.4] ]

Next, calculate the products (xix)(yiy)(x_i - \overline{x})(y_i - \overline{y}):

[ [-10 \times -4.6, -9 \times -3.6, -1 \times 0.4, 4 \times 3.4, 16 \times 4.4] = [46, 32.4, -0.4, 13.6, 70.4] ]

Sum of the products:

(xix)(yiy)=46+32.40.4+13.6+70.4=162\sum (x_i - \overline{x})(y_i - \overline{y}) = 46 + 32.4 - 0.4 + 13.6 + 70.4 = 162

Now, calculate (xix)2\sum (x_i - \overline{x})^2:

(10)2+(9)2+(1)2+42+162=100+81+1+16+256=454(-10)^2 + (-9)^2 + (-1)^2 + 4^2 + 16^2 = 100 + 81 + 1 + 16 + 256 = 454

Finally, calculate b1b_1:

b1=1624540.357b_1 = \frac{162}{454} \approx 0.357

Step 3: Calculate the Y-intercept (b0b_0)

b0=yb1x=5.60.357×335.611.7816.181b_0 = \overline{y} - b_1\overline{x} = 5.6 - 0.357 \times 33 \approx 5.6 - 11.781 \approx -6.181

Step 4: Equation of the Regression Line

y^=6.181+0.357x\hat{y} = -6.181 + 0.357x

Step 5: Correlation Coefficient (Optional)

This requires further calculation to determine if the correlation coefficient is statistically significant, which would indicate whether it's appropriate to use this regression line for prediction.

Would you like to continue with calculating the correlation coefficient, or do you have other questions related to this regression analysis?


Related Questions:

  1. How is the correlation coefficient calculated in this context?
  2. What does a positive or negative slope in a regression line indicate?
  3. How do you interpret the y-intercept in this regression model?
  4. What are the implications if the correlation coefficient is not statistically significant?
  5. How can you test the significance of the correlation coefficient?
  6. What is the meaning of the term "least squares" in regression analysis?
  7. How does the regression line minimize the sum of squared errors?
  8. Can you apply the regression model to data outside the given range of prices?

Tip: Always check the statistical significance of the correlation coefficient before using the regression line to make predictions.

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Math Problem Analysis

Mathematical Concepts

Regression Analysis
Linear Regression
Correlation Coefficient

Formulas

Regression line equation: ŷ = b₀ + b₁x
Correlation coefficient formula

Theorems

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Suitable Grade Level

Advanced High School