Models in Irrigation andWater Management - Practices of Irrigation and On-farm Water Management - page 418

Step 5

Arrange the yield data and weather elements (single or composite) for multiple
linear regression analysis as follows:

Yield rate (t/ha) Degree-day Rainfall (cm)

0.8601 1,270 37.5

0.8987 1,260 28.2

0.6962 1,292 8

0.7809 1,239 15.4

0.6667 1,276 40.8

0.6583 1,330 16.5

0.8273 1,217 45.2

0.7382 1,320 32

0.7415 1,305 73.5

0.6273 1,354 47.6

0.8530 1,175 68.6

0.8448 1,355 47.4

0.7687 1,364 25.6

0.6935 1,350 61.7

0.9006 1,314 39.5

0.8230 1,367 44.1

0.7924 1,325 43.3

0.7006 1,289 46.7

Step 6

Performmultiple regression analysis. The results (obtained through Microsoft Excel
tool) are as follows:

Summary output

Regression statistics
Multiple R 0.33849

R square 0.11458

Adjusted R square -0.00348

Standard error 0.08500

Observations 18

Standard
error

Lower
95%

Upper
95%

Lower
95.0%

Upper
95% Coefficients t stat P-value

Intercept 1.42676 0.508 2.807 0.013 0.343 2.510 0.343 2.510

X Variable 1 − 0.00052 0.000 − 1.335 0.202 − 0.001 0.000 − 0.001 0.000

X Variable 2 0.00035 0.001 0.301 0.767 − 0.002 0.003 − 0.002 0.003