Bayes' Theorem: Probability of 8 Heads in 10 Tosses?

AI Thread Summary
The discussion centers on calculating the likelihood term in Bayes' Theorem for a bent coin with a 60% chance of heads, specifically the probability of getting 8 heads in 10 tosses. Participants clarify that the initial approach of calculating the probability of 8 heads in a row is incorrect; instead, the binomial distribution should be used to account for various combinations of outcomes. The correct method involves summing the probabilities of all possible sequences that result in 8 heads and 2 tails. One user acknowledges the guidance received and confirms they are now using the binomial theorem to find the correct answer. The conversation emphasizes understanding the distinction between different probability scenarios in coin tosses.
Tajeshwar
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Homework Statement



Suppose I have a bent coin with a 60% probability of coming up heads. I throw the coin ten times and it comes up heads 8 times.

What is the value of the “likelihood” term in Bayes’ Theorem -- the conditional probability of the data given the parameter.

Homework Equations

The Attempt at a Solution



My attempt was 8 heads in a row should be (.6)^8... That comes to .0167. However, that is not one of the choices.

#4 almost matches, but there is a difference in the decimal.

The answer choices are:

0.120932
0.122885
0.168835
0.043945
[/B]
 
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The question is not asking you for the probability for the coin to comu up heads 8 times in a row. It is asking you for the probability for it to come up heas 8 times in 10 tosses.
 
Tajeshwar said:

Homework Statement



Suppose I have a bent coin with a 60% probability of coming up heads. I throw the coin ten times and it comes up heads 8 times.

What is the value of the “likelihood” term in Bayes’ Theorem -- the conditional probability of the data given the parameter.

Homework Equations

The Attempt at a Solution



My attempt was 8 heads in a row should be (.6)^8... That comes to .0167. However, that is not one of the choices.

#4 almost matches, but there is a difference in the decimal.

The answer choices are:

0.120932
0.122885
0.168835
0.043945[/B]
(1) Please stop using bold font; it looks like you are yelling at us.
(2) There are many "sample points" in the event "E = {8 heads in 10 tosses}"; for example, three possible outcomes in E would be HHHHHHHHTT or TTHHHHHHHH or THTHHHHHHH, and there are several others as well. To get the probability of 8 heads you need to compute each such probability and then add them all up! There is a very familiar probability distribution associated with such problems, and you can very likely get a lot of relevant information by reading your textbook or course notes. Google is your friend as well.
 
Ray Vickson said:
(1) Please stop using bold font; it looks like you are yelling at us.
(2) There are many "sample points" in the event "E = {8 heads in 10 tosses}"; for example, three possible outcomes in E would be HHHHHHHHTT or TTHHHHHHHH or THTHHHHHHH, and there are several others as well. To get the probability of 8 heads you need to compute each such probability and then add them all up! There is a very familiar probability distribution associated with such problems, and you can very likely get a lot of relevant information by reading your textbook or course notes. Google is your friend as well.

Sorry about the bold font. I did not realize that was offensive or I was even doing it. Thank you for pointing it out.

I also appreciate your guidance on this question.

I tried the binomial theorem for exactly 8 heads and that has led me to one of the choices. So that is what they must be asking. Let me see if it works out.

I think the general level of people on this forum is quite advanced and that is why my questions may seem a little too simplistic. Hopefully, I will keep learning and get there slowly.
 
Orodruin said:
The question is not asking you for the probability for the coin to comu up heads 8 times in a row. It is asking you for the probability for it to come up heas 8 times in 10 tosses.

Yes thank you. That helped. Appreciate your guidance.
 
Since ##px^9+q## is the factor, then ##x^9=\frac{-q}{p}## will be one of the roots. Let ##f(x)=27x^{18}+bx^9+70##, then: $$27\left(\frac{-q}{p}\right)^2+b\left(\frac{-q}{p}\right)+70=0$$ $$b=27 \frac{q}{p}+70 \frac{p}{q}$$ $$b=\frac{27q^2+70p^2}{pq}$$ From this expression, it looks like there is no greatest value of ##b## because increasing the value of ##p## and ##q## will also increase the value of ##b##. How to find the greatest value of ##b##? Thanks
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