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Experimental — or empirical probability Question

Screen Link:
https://app.dataquest.io/m/377/estimating-probabilities/3/probability-as-relative-frequency


What I expected to happen:
Where I double-check online I see the Formula is
p_heads_1 = number of times event E happened / number of times we repeated the experiment
should be
p_heads_1 = 162 / 300 = 0.54

What actually happened:
In this exercise, We tossed a coin 300 times and got tails 162 times.
I’m trying to understand why the response is:
p_heads_1 = (300-162) / 300


Thanks

The key thing to notice here is that the experiment produced 162 TAILS out of 300 trials. This means that HEADS occurred (300-162)=138 times. And since we are trying to calculate the probability of heads (i.e. p_heads_1) we should use (300-162)=138 in our calculation.

EDIT_1:
Alternatively, since p_heads + p_tails must equal 100%, we could also calculate p_heads_1 using:

p_heads_1 = 1 - 162/300
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