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Exercise

Hypothesis test: did earthquake frequency change?

Obviously, there was a massive increase in earthquake frequency once wastewater injection began. Nonetheless, you will still do a hypothesis test for practice. You will not test the hypothesis that the interearthquake times have the same distribution before and after 2010, since wastewater injection may affect the distribution. Instead, you will assume that they have the same mean. So, compute the p-value associated with the hypothesis that the pre- and post-2010 interearthquake times have the same mean, using the mean of pre-2010 time gaps minus the mean of post-2010 time gaps as your test statistic.

Instructions

100 XP
  • Compute the observed test statistic. The variables mean_dt_pre and mean_dt_post from previous exercises are in your namespace.
  • Shift the post-2010 data to have the same mean as the pre-2010 data. Store the result as dt_post_shift.
  • Draw 10,000 bootstrap replicates each of mean of dt_pre and dt_post_shift. Store the respective results in bs_reps_pre and bs_reps_post.
  • Compute replicates of difference of means by subtracting bs_reps_post from bs_reps_pre.
  • Compute and print the p-value. Consider "at least as extreme as" to be that the test statistic is greater than or equal to what was observed.