Correlation and Least Square Regression: A long term study of changing environmental conditions in Chesapeake Bay found the following annual average salinity readings in one location in the bay:
Year Salinity (%)
1971 13.4
1972 9.8
1973 15.1
1974 14.7
1975 15.1
1976 14
1977 15.7
1978 16
1979 16
1980 13.8
1981 17.9
1982 20
1983 16
1984 15.4
a) Make a plot of salinity against time. Was salinity generally increasing or decreasing over these years? Is there an overall straight line tend over time?
b) What is the correlation between salinity and year/ What percentage of the observed variation in salinity is accounted for by straight line change over time?
c) Find the least squares regression line for predicting salinity from year. Explain in simple language what the slope of this line tells your about Chesapeake Bay.
d) If the rend in these past data had continued, what would be the average salinity at this point in the bay in 1988?
Year Salinity (%)
1971 13.4
1972 9.8
1973 15.1
1974 14.7
1975 15.1
1976 14
1977 15.7
1978 16
1979 16
1980 13.8
1981 17.9
1982 20
1983 16
1984 15.4
a) Make a plot of salinity against time. Was salinity generally increasing or decreasing over these years? Is there an overall straight line tend over time?
b) What is the correlation between salinity and year/ What percentage of the observed variation in salinity is accounted for by straight line change over time?
c) Find the least squares regression line for predicting salinity from year. Explain in simple language what the slope of this line tells your about Chesapeake Bay.
d) If the rend in these past data had continued, what would be the average salinity at this point in the bay in 1988?
