Probability of scoring a penalty

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    Probability
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Discussion Overview

The discussion revolves around calculating the probability of scoring less than 50% when taking 10 penalties, given a scoring probability of 2/5 for each penalty. The focus is on the mathematical reasoning and calculations involved in determining this probability.

Discussion Character

  • Mathematical reasoning

Main Points Raised

  • One participant states the probability of scoring a penalty is 2/5 and poses a question about the probability of scoring less than 50% out of 10 attempts.
  • Another participant proposes a formula involving combinations and probabilities to calculate the desired probability, though they note they have not thoroughly checked it.
  • A subsequent reply suggests that the calculation yields an approximate answer of 0.633, which they find reasonable.
  • A later post claims to have verified that the calculation provided is indeed correct.

Areas of Agreement / Disagreement

There appears to be a general agreement on the method of calculation and the resulting probability, although the initial proposal was not thoroughly checked by the participant who presented it.

Contextual Notes

The discussion does not clarify the assumptions behind the calculations, such as the independence of penalty attempts or the specific definitions of scoring less than 50%.

urbantrained
The probability that I take a penalty and score is 2/5.

If I take 10 penalties, what is the probability that I score less than 50% of them?
 
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My gut instinct tells me the answer should be:

(10!/4!6!)(3/5)6(2/5)4 + (10!/3!7!)(3/5)7(2/5)3 + (10!/2!8!)(3/5)8(2/5)2 + (10!/9!)(3/5)9 2/5 + (3/5)10

but I've not checked it throughly
 
Last edited:
The above gives an answer of ~0.633 which seems about right to me.
 
I've just done a quick check and the above is indeed the correct answer.
 

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