Minitab - Statistics correlation worksheet
Statistics I - Adiletta 1
Statistics Correlation Worksheet Name: _________________________
Ice Cream Sales
Answer the following questions, showing any calculations involved. Include this document along with the graphs created with Minitab in your submission.
1. Identify the independent (predictor) and dependent (response) variables. [2 pts]
Independent variable: __________________ Dependent variable: __________________
2. From the scatter diagram, does there seem to be a linear correlation? If so, is it strong or weak? Is it positive or negative? What does it say about the relationship between the 2 variables? [4 pts]
3. Use your scatter diagram to answer the following questions.
a. If you calculated the linear correlation coefficient for this data to be r = –0.75, explain in one sentence how you know this is incorrect. [2 pts]
b. If you calculated the linear correlation coefficient for this data to be r = 1.20, explain in one sentence how you know this is incorrect. [2 pts]
4. What is the correlation coefficient, r. Based on the correlation coefficient, how accurate do you think your regression equation is at making a prediction? Why? [2 pts]
5. What is the p-value? Is a linear relationship appropriate? How do you know? [2 pts]
6. Identify the following quantities: [3 pts]
Regression Equation: ______________________________
Slope: _______________ y-Intercept: _______________
7. Explain the meaning of the slope in terms of this problem. [5 pts]
8. Explain the meaning of the y-intercept in terms of this problem. Is it meaningful? Why or why not? [5 pts]
9. Predict the ice cream cone sales on a day where the high temperature was 75°. Show all work here and round to 2 decimals. [2 pts]
10. On a 70° day, the Creamery had sales of 400 ice cream cones. Is this sales figure above or below the average for this temperature? Show your work for credit. [2 pts]
11. Answer the following questions.
a. The high temperature on Saturday is predicted to be 75°. Would it be reasonable to use the regression equation you created to predict this day’s sales? Why or why not? [2 pts]
b. The high temperature on Sunday is predicted to be 85°. Would it be reasonable to use the regression equation you created to predict this day’s sales? Why or why not? [2 pts]
c. The high temperature on Sunday at the Creamery’s Buffalo store is predicted to be 74°. Would it be reasonable to use the regression equation you created to predict this store’s sales? Why or why not? [2 pts]
12. Compute and interpret R2. [4 pts]
Minitab Commands:
Correlation
Stat > Basic Statistics > Correlation
Enter both variables > OK
Regression Analysis
Stat > Regression > Regression > Fit Regression Model
Responses: Enter response variable
Continuous predictors: Enter predictor variable > OK
Fitted Line Plot & Regression Equation
Stat > Regression > Fitted Line Plot
Enter Response and Predictor variables > OK
To create a Residual Plot in Minitab
Stat > Regression > Fitted Line Plot.
Enter Response and Predictor variables
Be sure Type of Regression Model is Linear
Graphs > In the cell that says “Residuals versus the variables,” enter the name of the explanatory variable. OK > OK