Quiz 2 Regression

1. (3 points) Suppose we were interested in answering the question: ’Does a student’s use of the social platform TikTok influence the amount of sleep they ultimately get?’

(a) What is the Explanatory variable in this scenario? Explain how you know.

(b) What is the Response variable in this scenario? Explain how you know.

2. (3 points) The scatter plot of three different data set is given below. Some of their correlation coefficients appear below

r = −1    r = −0.64    r = 0.07    r = 0.31    r = 0.83    r = 0.99    r = 1

Explain which of the correlation coefficients matches the graph, be sure to use at least one sentence in explaining how you know that is the correct correlation coefficient.

Use the link in Canvas to obtain the data set. Use the data to complete the following questions!
Perhaps you are familiar with the famous Old Faithful geyser in Yellowstone National Park. Another Old Faithful geyser is located in Calistoga in California’s Napa Valley. The following data represent the time (in minutes) between eruptions and the length of eruption for 9 randomly selected eruptions.

(a) (2 points) Find and sketch the scatter diagram below. Write the commands you use to produce the graph.

(b) (2 points) Find the correlation coefficient and use it to show there is a significant relationship. 
Hint: Critical Value!

(c) (2 points) Find the equation of the least-square line. Why do we want to find the equation of the line? That is, why do we use the equation of the line?

(d) (2 points) Find the predicted length of eruption if we let the time between eruptions be 14 minutes. Show the work by hand or write the command you used.