Question

A department of transportation’s study on driving speed and miles per gallon for midsize automobiles resulted in the following data:

Speed (Miles per Hour)Miles per Gallon: 30 51 39 55 30 24 61 24 50 56

Miles per Gallon: 29 25 25 23 31 33 20 35 26 24

Compute the sample correlation coefficient (to 2 decimals and enter negative value as negative number).

What can you conclude, based on your computation of the sample correlation coefficient?

Answer 1

	x	y	x^2	y^2	xy
	30	29	900	841	870
	51	25	2601	625	1275
	39	25	1521	625	975
	55	23	3025	529	1265
	30	31	900	961	930
	24	33	576	1089	792
	61	20	3721	400	1220
	24	35	576	1225	840
	50	26	2500	676	1300
	56	24	3136	576	1344
Total	420	271	19456	7547	10811

Correlation coefficient

=-0.94

Therefore, we an conclude that , there is very strong negative correlation between  driving speed and miles per gallon

We can directly calculate correlation coefficient by using Excel.

Step 1)  Enter data in Excel.

Step 2 )  Then use =CORREL command and select two separate column data  >> ok