Joan is concerned about the amount of energy she uses to heat her home. The graph below plots the mean number of cubic feet of gas per day that Joan used each month against the average temperature that month (in degrees Fahrenheit) for one heating season.

(a) Does the plot show a positive or negative association between the variables? Why does this make sense?

(b) What is the form of the relationship? Is it very strong? Explain your answers.

(c) Explain what the point at the bottom right of the plot represents.

The graph below plots the mean number of cubic feet of gas per day.

As the temperature (the explanatory variable) increases, the amount of gas consumed (the response variable) will decrease as the house is naturally warmer by the temperature. Read a scatter plot from left to right, if the points are drifting in the downward direction the scatter plot shows a negative association. Another way to determine a negative correlation is if either variable increases as the other variable decreases.

The graph below plots the mean number of cubic feet of gas per day.

The points in the scatterplot seem to roughly line on a line and thus the relationship between the variable is roughly linear. Since the linear pattern is obvious from the scatterplot, the relationship is also strong.

The graph below plots the mean number of cubic feet of gas per day.

The point at the right bottom describes a month where the average temperature was about $58$ degrees Fahrenheit and there are approximately $250$ cubic feet of gas consumed that month.