)'s review 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.