Check Your Understanding:
You've probably heard the saying "Practice makes perfect!", but does practice also help you
complete a task faster? A study was conducted to find out. A random sample of 15 high school
students were taught how to solve a Rubik's cube. Then they were each randomly assigned a
number of times to practice this new skill. After they completed their assigned number of practices
they were timed solving the Rubik's cube. Here is a scatterplot of the results along with the least-
squares regression line.
a. Describe the influence the student who was assigned
to practice following the steps to solve a Rubik's cube
14 times has on the equation of the least-squares
regression line.
10
b. Describe the influence the student who was assigned to practice following the steps to solve a
Rubik's cube 14 times has on the standard deviation of the residuals and 2
C. The mean and standard deviation of the number of practices are x = 8 practices and sx =
4.47 practices. The mean and standard deviation of time are y = 7.71 minutes and Sy =
1.20 minutes. The correlation between number of practices and time to solve the Rubik's
cube is r=-0.793. Find the equation of the least squares regression line for predicting time
to solve the Rubik's cube from the number of practices.