Chapter 10.2, Problem 25BSC

Testing for a Linear Correlation. In Exercises 13-28, construct a scatterplot, and find the value of the linear correlation coefficient r. Also find tire P-value or the critical values of r from Table A-6 using α = 0.05. Determine whether there is sufficient evidence to support a claim of a linear correlation between the two variables. (Save your work because the same data sets will be used in Section l0-3 exercises.)

25. Gas Prices Cat prices have been very volatile in recent years. The table below lists gas prices (dollars per gallon) at randomly selected Connecticut stations at the time of this writing (based on data from AOL Autos). Is there sufficient evidence to conclude that there is a linear correlation between prices of regular gas and prices of premium gas? For the gas stations that sometimes post only the price of regular gas, can you use those prices to get a good sense of the price of premium gas?

Regular	2.77	2.77	2.79	2.81	2.78	2.86	2.75	2.77
Mid-Grade	3.00	2.77	2.89	2.93	2.93	2.96	2.86	2.91
Premium	3.07	3.09	3.00	3.06	3.03	3.06	3.02	3.03