Minitab Solution Printout for the Water/Temperature example. 

At this time, we will only use the "R-Sq = 99.4%" which is highlighted in yellow in the Minitab solution printout below.    

Once you find R-Sq you need to take the square root of the number because we are interested in R and not R-Sq.

Interpretation

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Regression Analysis
The regression equation is
Water Consumption = - 122 + 12.5 Time mowing + 1.51 Temperature

Predictor  Coef      StDev       T       P
Constant   -121.655  6.540      -18.60 0.000
Time mow  12.532    1.933      6.48   0.003
Temperat  1.51236   0.06077    24.89  0.000

S = 1.245 R-Sq = 99.4% R-Sq(adj) = 99.0%

Analysis of Variance
Source         DF    SS     MS     F      P
Regression     2     970.66 485.33 313.17 0.000
Residual Error 4     6.20   1.55
Total          6     976.86

Source   DF Seq SS
Time mow 1  10.88
Temperat 1  959.78 


Learn the Procedure for calculating correlation coefficients