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 29 33 34 36 46 Number of Bids 1 3 8 9 10 Table

Step 1 of 6 : Find the estimated slope. Round your answer to three decimal places.

Solution

To find the estimated slope (b1b_1) of the regression line, we will use the formula for the slope of the least squares regression line:

b1=nxiyixiyinxi2(xi)2b_1 = \frac{n \sum{x_i y_i} - \sum{x_i} \sum{y_i}}{n \sum{x_i^2} - (\sum{x_i})^2}

Where:

  • xix_i are the values of the independent variable (price),
  • yiy_i are the values of the dependent variable (number of bids),
  • nn is the number of data points.

Let's start by organizing the data:

Price (xx)Number of Bids (yy)xyx \cdot yx2x^2
29129841
333991089
3482721156
3693241296
46104602116

Now, calculate the necessary sums:

  • xi=29+33+34+36+46=178\sum{x_i} = 29 + 33 + 34 + 36 + 46 = 178
  • yi=1+3+8+9+10=31\sum{y_i} = 1 + 3 + 8 + 9 + 10 = 31
  • xiyi=29+99+272+324+460=1184\sum{x_i y_i} = 29 + 99 + 272 + 324 + 460 = 1184
  • xi2=841+1089+1156+1296+2116=6498\sum{x_i^2} = 841 + 1089 + 1156 + 1296 + 2116 = 6498
  • n=5n = 5

Substitute these values into the slope formula:

b1=5×1184178×315×6498(178)2b_1 = \frac{5 \times 1184 - 178 \times 31}{5 \times 6498 - (178)^2}

Now, let's calculate this step by step:

b1=592055283249031684b_1 = \frac{5920 - 5528}{32490 - 31684}

b1=392806b_1 = \frac{392}{806}

b1=0.486b_1 = 0.486

Thus, the estimated slope (b1b_1) is 0.486 (rounded to three decimal places).


Would you like further details or explanations on any steps? Feel free to ask!

Here are some related questions for you:

  1. How do you calculate the estimated intercept b0b_0 in the regression line?
  2. How would you calculate the correlation coefficient for this data?
  3. What is the significance of the slope in this context?
  4. How do you interpret the regression line for predicting the number of bids?
  5. Why is it important to check if the correlation coefficient is statistically significant?

Tip: Always check the significance of the regression model (using hypothesis tests) before making predictions to ensure reliability.

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Math Problem Analysis

Mathematical Concepts

Statistics
Linear Regression
Correlation
Least Squares Method

Formulas

b1 = (n Σ(xi yi) - Σxi Σyi) / (n Σ(xi^2) - (Σxi)^2)

Theorems

Least Squares Regression Theorem

Suitable Grade Level

Grades 11-12