In Chapter 7, (Data in Tompkins County Bridges 2014) we found a relationship between the age of a bridge in Tompkins County, New York, and its condition as found by inspection. But we considered only bridges built or replaced since 1886. Tompkins County is the home of the oldest covered bridge in daily use in New York State. Built in 1853, it was recently judged to have a condition of 4.57.

Dependent variable is Condition
R-squared = 43.4% s = 0.7236
Variable Coefficient
Intercept €¦€¦€¦€¦€¦€¦.. -37.7775
Year €¦€¦€¦€¦€¦€¦€¦€¦. 0.02190
a) If we use this regression to predict the condition of the covered bridge, what would its residual be?
b) If we add the covered bridge to the data, what would you expect to happen to the regression slope? Explain.
c) If we add the covered bridge to the data, what would you expect to happen to the R2? Explain.
d) The bridge was extensively restored in 1972. If we use that date instead, do you find the condition of the bridge remarkable?

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1900 1920 1940 1960 1980 2000 Year