A regional sales manager records data on the number of clients a salesperson contacts in a week (x) and the total sales generated that week (y). The data from 10 salespeople is shown below. Find the equation of the regression line and use it to predict sales if the salesperson contacts (a) 6 clients; (b) 40 clients
Table of contents
- 1. Introduction to Statistics53m
- 2. Describing Data with Tables and Graphs2h 1m
- 3. Describing Data Numerically1h 48m
- 4. Probability2h 26m
- 5. Binomial Distribution & Discrete Random Variables2h 55m
- 6. Normal Distribution & Continuous Random Variables1h 48m
- 7. Sampling Distributions & Confidence Intervals: Mean2h 8m
- 8. Sampling Distributions & Confidence Intervals: Proportion1h 20m
- 9. Hypothesis Testing for One Sample2h 23m
- 10. Hypothesis Testing for Two Samples3h 25m
- 11. Correlation1h 6m
- 12. Regression1h 4m
- 13. Chi-Square Tests & Goodness of Fit1h 30m
- 14. ANOVA1h 4m
12. Regression
Linear Regression & Least Squares Method
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The scatterplot below shows a set of data and its least-squares regression line. Based on the graph, which of the following is most likely the equation of the regression line?

A
y^=4.1x+50.9
B
y^=−10.2x+50.9
C
y^=−4.1x+50.9
D
y^=−4.1x−50.9

1
Step 1: Observe the scatterplot and the regression line. The regression line has a negative slope, as it decreases from left to right. This indicates that the relationship between x and y is negative.
Step 2: Recall the general form of a linear regression equation: ŷ = mx + b, where m is the slope and b is the y-intercept. A negative slope means m < 0.
Step 3: Identify the y-intercept from the graph. The regression line intersects the y-axis at approximately 50, which suggests that b = 50.9 in the equation.
Step 4: Compare the slope visually. The line decreases steeply, suggesting a slope magnitude closer to -4.1 rather than -10.2. This eliminates options with incorrect slopes.
Step 5: Based on the negative slope and the correct y-intercept, the most likely equation of the regression line is ŷ = -4.1x + 50.9.
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