The test results of the unit root of the variable show that most of the data unit root tests are not significant, so we have a

first-order difference unit root test for these data, the sequence of the first order difference unit root test results are obtained.

The results of the unit root test for first-order difference variables, except for that ofthe price index logarithm and trade liberalization logarithm, are shown in Table 2.

Table (2): unit root test for first-order difference Logarithm variables

Non-stationary time series data are normally predictive only within a shorter episode, hence are not considered the an appropriate tool in forecasting (Gujarati and Porter, (10)) If the original time series is non-stationary, the

first-order difference often becomes stationary.

Mathematical topics covered include Markov chains, matrix algebra and linear and nonlinear

first-order difference equations.

However, they said, "It seems clear that there is a

first-order difference in the nature of Earth surface Cr cycling" before and after the rise of animals.

Hypothesis 1a: The

first-order difference of the slope function with respect to time will be negative until [T.

So we should firstly implement difference on the series to get the

first-order difference series graph (see figure 2).

DELTA] represents

first-order difference, P represents lag periods.

Our Granger-causality tests are therefore conducted on the

first-order difference of these time series.

This results in first-order noise evidenced by the

first-order difference operation on Tstop.

The various

first-order differences combine to produce a clearer pattern of difference between males and females for the second-order factors.