Question

The accompanying data were read from graphs that appeared in an article. The variables shown are the number of acres burned in forest fires in the western United States and timber sales.

Year	Number of Acres Burned (thousands)	Timber Sales (billions of board feet)
1945	208	2.2
1950	254	3.6
1955	260	4.3
1960	379	6.8
1965	85	9.9
1970	444	11.0
1975	174	11.1
1980	246	10.4
1985	438	9.9
1990	410	11.0
1995	182	3.7

(a) Compute the correlation coefficient. (Give the answer to three decimal places.)
r =
Is there a correlation between timber sales and acres burned in forest fires?

strong positive correlationweak positive correlation    strong negative correlationweak negative correlationno correlation

(b) The article concludes that "heavier logging led to large forest fires." Do you think this conclusion is justified based on the given data?

YesNo

Answer 1

a)

correlation coefficient r=

Sxy/(√Sxx*Syy) =

0.307

weak positive correlation

b)

Since above study is observational , correlation does not indicate causation.

Therefore the conclusion is not justified.

No