if the test statistic of ad fuller test is less than the critical value( )we reject the null hypothesis of nonstationarity the ad fuller test is available as part of the statsmodel library since it is quite evident that our original series of gold prices is non-stationarywe will perform log transformation and see if we are able to obtain stationarity the following snippet uses the rolling stats plots and ad fuller tests to check the same in [ ]log_series np log(gold_df valuead_fuller_test(log_seriesplot_rolling_stats(log_seriesthe test statistic of - is greater than either of critical valueshence we fail to reject the null hypothesisi the series is non-stationary even after log transformation the output and plot depicted in figure - confirm the same test statistic - -value #lags used number of observations used critical value ( %- critical value ( %- critical value ( %- dtypefloat figure - rolling mean and standard deviation plot for log transformed gold price