Hot Chocolate Experiment

Have you ever stirred your hot chocolate and noticed that the pitch increases as you continue to tap?  Here are recordings of the tapping sound under different conditions.

Condition #1: Does the cup's composition impact the change in pitch?

Here we tested 3 different kinds of cups: a normal-shaped one, a wide one, and a tallish plastic one.

Null Hypothesis:  There is no substantial difference in the tapping pitch characteristics among different kinds of mugs.

Here are recordings of what the tapping sounded  like for each cup when the mug was filled with fresh cocoa:

  1. Regular mug with freshly mixed hot cocoa


  • After listening to these recordings, do you think the null hypothesis true or false? 
  • If the null hypothesis is true, what can you conclude?  If the null hypothesis is false, what can you conclude?  In other words, does the composition of the mug affect (or not affect) the changes in tapping pitch?
  • If this null hypothesis is true, then what other conditions might we test?
  • Null hypotheses are usually associated with quantitative data.  In this case, we are using qualitative data.  Is it valid to apply a null hypothesis to qualitative data?  Why or why not?

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