Here we could use both parametric or non-parametric tests. Thanks to my peer Unisse Chua (uc288) 's review, I found her recommendation very useful and resonable. Since the sample came from the same population of Citibike users with paired data and there were at least 30 observations per sample, we could apply a z-test for two proportions to test the hypothesis.  However, now that the comparison given was between ratios and a priori expectation is being done, based on the chart from the slides, the test to be used could also be the chi-squared goodness of fit test with Yate's correlation or Fischer's exact test.  And for a chi-square test for equality of two proportions is exactly the same thing as a Z-test and due to function convenience in iPython, I was using a z-test.