Kata

The description uses an incorrect terminology: "mutually exclusive events" should be replaced with "independent events" everywhere. The joint probability of mutually exclusive events is always 0. But the joint probability of independent events is the product of probabilities.

• Python new test framework should be used (Refer this & this for more detail)

• test.assert_approx_equals should be used instead

• Node 12 should be enabled (Refer this and this for more info)

• assert.approxEquals should be used instead

Ruby 3.0 should be enabled, see this to learn how to do it

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Who's the jerk who put a link into the description that leads directly to the EDIT PANEL of the other kata...?

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This is now faulty for python without replacement

I did the math longhand and it worked fine, but failed the third random case. The expected value was not the correct value based on doing the math long form.

Any idea why that might be?

problem was: (ball_probability([['yellow', 'green', 'yellow', 'yellow', 'yellow', 'yellow', 'green', 'green', 'blue', 'green', 'green', 'blue', 'red'], ['green', 'blue'], False]))

I have a feeling I am missing something in the explantion. All the test cases work fine, but when I run on random inputs I sometimes get failures when replace is False. So let me talk you through my understanding of one test case (w/o showing the code) (... and as you will see I am not a mathematician so I need dummies guide as explantions!)

The input is [['red', 'yellow', 'red', 'yellow', 'yellow', 'blue', 'red', 'yellow', 'green', 'blue', 'blue', 'green', 'red', 'yellow', 'yellow', 'green', 'yellow', 'blue'], ['blue', 'red'], False]

So I have 18 balls, 4 of which are blue, so P(b) = 4/18 = 0.222.... Since I don't replace the blue that I drew on the first round, I now have only 17 balls, 4 of which are red, so P(r) = 4/17 = 0.235...

So P(b,r,False) = 0.222x0.235 = 0.052, but according to the test, the probablity should be 0.037

Now - where is the flaw? I was hoping writing this would lead me to enightenment, but not the case this time...

My solution failed one of the random test cases; the kata "expected -0 but got 0". It went through fine when I hit submit a second time.

Translations published :)

I tried to keep your original spirit intact, so same data structure as an input and not too many edge test cases (no balls with less than 2 elements); let me know if everything is ok for you!