The lady tasting iced tea

As part of the parents involvement in my youngest son school, last Friday was the “parents teaching” day, where parents presented various topics that may interest the students. I chose to try the reproduce Fisher’s lady tasting tea experiment, but with a twist.

I started the class with general discussion on designing experiments, and presented the story of the lady and the tea. Then I asked them how they would test if the lady can actually tell whether the tea or the milk was added first to a cup. After a short discussion, the 11 years old students reached the design that Fisher used. Of course, I did not expect them to get into the statistical inference details.

Once we got a design, I pooled two bottles of iced tea out of my bag. In Israel there are two leading brands of iced tea, lets call them A and B. A few more minutes were needed to get to the design of an experiment for testing whether the kids can distinguish between the tastes of the two brands.

We used the following design:

  1. A flip of a coin determined if we will pour the same brand of iced tea into two cups, or pour one brand in one cup and the other brand into the other cup.
  2. In case the same brand should be poured into the two cups, another coin flip determined if it should be brand A or brand B.

Then, one of the students who was, of course, blinded to the process of filling the cups, tasted the tea in both cups and announced if she can distinguish between the tastes of the tea in each cup, and her answer was recorded.

The final results are [*]:

Was the taster right?
Yes No Total
Cups combination AB 5 5 10
AA or BB 4 3 7
Total 9 8 17

I think we can conclude that there is no evidence for rejecting the hypothesis that the students can distinguish between the tastes of the two brands (you are welcome to do your own statistical analysis).

On a personal note: from my point of view it was a great success, since my son, who refused tasting brand B was convinced to taste it, and admitted that he likes its taste.

[*] I know I should have recorded the outcomes of the re-randomization, so that the table will have 3 rows and not only two. You will have to forgive me. My only excuse is that was a fun demonstration for fifth graders.

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