International Scholarly Research Notices

Research Article

A Combined Model of Global Cultivated Area Change and Prediction for Future: 1961–2020

Table 7

Unit root test results of irregular part in global cultivated series.
Test typeTrend form Adjusted value1%5%10%Judgment
ADFWithout C, without T −3.03−2.62−1.95−1.61Stationary
PPWithout C, without T −2.34−2.62−1.95−1.61Stationary
Note: means intercept term, and T means trend term with time. Unit root test equation often has three forms: with intercept term but without trend term, with intercept term and with trend term, without intercept term and without trend term. Statistical test shows that the series of irregular part of global cultivated area has no trend and intercept terms.