#I learned alot from his answers because he uses theories to support his answers. I understand the uses of these theories from his answers.For example, when he explain that before we start the ADF testing we need to determine the appropriate lag length to select based on this time series data set. he said that care must be taken to ensure that an appropriate lag length is chosen. If the lag length is too short then the residuals will be serially correlated and the test will be biased. If the lag length is too large the power of the test will suffer. There is some literate precedence to suggest, based on boot strapping the lag length, that erring on the side of too large is better than erring on the side of too short.
#In question 3,from his data , he does not use Log Transform the data because no exponential growth . Also from data he said that There does not appear to be an noticeable trend in the data.