Bivariate Data

At a restaurant, the amount of tip for the waitress or waiter is automatically calculated at 20% of the bill total. The graph below shows the amount a tip would be for 6 different bill totals. 

A different restaurant does not automatically calculate the tip amount, but rather, the customers determine how much they want to leave as a tip. The graph below shows the amount of tip that 14 different customers left, based on the amount of their bill. 

A line has been drawn to represent the trend in data. The equation for the line is: $${y=0.14x+2.5}$$.

1. What does the 0.14 mean in this situation?
   1. The average tip amount is $0.14.
   2. On a $1 bill, the tip amount is estimated at $0.14.
   3. A $1 increase in the bill total is associated with a $0.14 increase in tip amount.
   4. A $0.14 increase in the bill total is associated with a $1 increase in tip amount.
2. What does the 2.5 mean in this situation?
   1. The average bill amount is $2.50.
   2. The equation predicts a $2.50 tip on a $0 bill.
   3. The equation predicts a $0.14 tip on a $2.50 bill.
   4. A $1 increase in the bill total is associated with a $2.50 increase in tip amount.
3. If a bill is $75.80, what prediction can a waiter or waitress make about the amount of the tip?

After giving a test, a teacher was curious to know if there was a relationship between how a student performed on the test and how long the student spent studying. She collected data from her classes and represented it in the scatter plot below.

She found a line that best fit the data and determined the equation for the line to be: $${y=0.8x+59}$$.  Which of the statements below are fair conclusions that she can make about her model? Select all that apply.

A city collected data on the percent of adults who smoked cigarettes. They collected this data from 1970 to 2010. The scatter plot below shows the data over time.

A line is drawn to represent the trend in the data, and the equation for the line is $$y=-0.57x+37.1$$.