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Is this an application case of Bayes theorem? Is my book wrong?


Bayes theorem applicationAn explanation of how this solution is derivedGoing wrong with Bayes theoremApplication of Bayes-theoremBasic application of Bayes theoremRoot estimator to get variance?Is this application of Bayes' theorem correct?Problem based on law of total probability and bayes theoremBayes theorem in geneticsBayes' Theorem, what am I doing wrong?













3












$begingroup$


A sickness has a heterozygote frequency of $frac120$ ie. 1 in 20 people of a population will have the allele combination $Aa$ where a denotes the recessive and A the dominant allele. To become sick the carrier needs to have two $aa$ alleles.



A mother is known to have the combination $Aa$ , what is the probability her child will be sick (have $aa$) if the combination of the husband is unknown (i.e. $AA, Aa, aa)$?



Now here is where I struggle. If the husband has $AA$ , the child will never get $aa$, if the husband has $Aa$, the child will get $aa$ with a chance of $frac14$.



If the husband has $aa$ (is sick himself) then the child wil get $aa$ with a chance of $frac12$



The book states that the answer a priori is for the child to be sick in this situation is $frac120 frac12 frac12 = frac180$



Shouldn't it instead be : $frac14frac120 + (textbfdouble aa frequency)cdot frac12$?










share|cite|improve this question









New contributor




Jonathan Maximilian is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







$endgroup$











  • $begingroup$
    Maybe the implication is that if the husband's combination is unknown, it must mean that he does not have $aa$, since he would have shown symptoms already? Is the "(i.e., $AA, Aa, aa$)" yours, or the book's?
    $endgroup$
    – Brian Tung
    yesterday











  • $begingroup$
    mine, and your answer makes a lot of sense lol, but my assumption is correct if aa was included ?
    $endgroup$
    – Jonathan Maximilian
    yesterday










  • $begingroup$
    actually i rechecked, and the book doesnt say anything about the husband showing early symptoms, it just says that the probability a priori is what i wrote in my post (1/80)
    $endgroup$
    – Jonathan Maximilian
    yesterday










  • $begingroup$
    Yeah, I don't know. Is the book online by any chance?
    $endgroup$
    – Brian Tung
    yesterday










  • $begingroup$
    no and its not in english lol, do you know if my attempt is correct? can you just sum the two probability trees together?
    $endgroup$
    – Jonathan Maximilian
    yesterday















3












$begingroup$


A sickness has a heterozygote frequency of $frac120$ ie. 1 in 20 people of a population will have the allele combination $Aa$ where a denotes the recessive and A the dominant allele. To become sick the carrier needs to have two $aa$ alleles.



A mother is known to have the combination $Aa$ , what is the probability her child will be sick (have $aa$) if the combination of the husband is unknown (i.e. $AA, Aa, aa)$?



Now here is where I struggle. If the husband has $AA$ , the child will never get $aa$, if the husband has $Aa$, the child will get $aa$ with a chance of $frac14$.



If the husband has $aa$ (is sick himself) then the child wil get $aa$ with a chance of $frac12$



The book states that the answer a priori is for the child to be sick in this situation is $frac120 frac12 frac12 = frac180$



Shouldn't it instead be : $frac14frac120 + (textbfdouble aa frequency)cdot frac12$?










share|cite|improve this question









New contributor




Jonathan Maximilian is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







$endgroup$











  • $begingroup$
    Maybe the implication is that if the husband's combination is unknown, it must mean that he does not have $aa$, since he would have shown symptoms already? Is the "(i.e., $AA, Aa, aa$)" yours, or the book's?
    $endgroup$
    – Brian Tung
    yesterday











  • $begingroup$
    mine, and your answer makes a lot of sense lol, but my assumption is correct if aa was included ?
    $endgroup$
    – Jonathan Maximilian
    yesterday










  • $begingroup$
    actually i rechecked, and the book doesnt say anything about the husband showing early symptoms, it just says that the probability a priori is what i wrote in my post (1/80)
    $endgroup$
    – Jonathan Maximilian
    yesterday










  • $begingroup$
    Yeah, I don't know. Is the book online by any chance?
    $endgroup$
    – Brian Tung
    yesterday










  • $begingroup$
    no and its not in english lol, do you know if my attempt is correct? can you just sum the two probability trees together?
    $endgroup$
    – Jonathan Maximilian
    yesterday













3












3








3


1



$begingroup$


A sickness has a heterozygote frequency of $frac120$ ie. 1 in 20 people of a population will have the allele combination $Aa$ where a denotes the recessive and A the dominant allele. To become sick the carrier needs to have two $aa$ alleles.



A mother is known to have the combination $Aa$ , what is the probability her child will be sick (have $aa$) if the combination of the husband is unknown (i.e. $AA, Aa, aa)$?



Now here is where I struggle. If the husband has $AA$ , the child will never get $aa$, if the husband has $Aa$, the child will get $aa$ with a chance of $frac14$.



If the husband has $aa$ (is sick himself) then the child wil get $aa$ with a chance of $frac12$



The book states that the answer a priori is for the child to be sick in this situation is $frac120 frac12 frac12 = frac180$



Shouldn't it instead be : $frac14frac120 + (textbfdouble aa frequency)cdot frac12$?










share|cite|improve this question









New contributor




Jonathan Maximilian is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







$endgroup$




A sickness has a heterozygote frequency of $frac120$ ie. 1 in 20 people of a population will have the allele combination $Aa$ where a denotes the recessive and A the dominant allele. To become sick the carrier needs to have two $aa$ alleles.



A mother is known to have the combination $Aa$ , what is the probability her child will be sick (have $aa$) if the combination of the husband is unknown (i.e. $AA, Aa, aa)$?



Now here is where I struggle. If the husband has $AA$ , the child will never get $aa$, if the husband has $Aa$, the child will get $aa$ with a chance of $frac14$.



If the husband has $aa$ (is sick himself) then the child wil get $aa$ with a chance of $frac12$



The book states that the answer a priori is for the child to be sick in this situation is $frac120 frac12 frac12 = frac180$



Shouldn't it instead be : $frac14frac120 + (textbfdouble aa frequency)cdot frac12$?







statistics bayes-theorem






share|cite|improve this question









New contributor




Jonathan Maximilian is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











share|cite|improve this question









New contributor




Jonathan Maximilian is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









share|cite|improve this question




share|cite|improve this question








edited yesterday









rash

20811




20811






New contributor




Jonathan Maximilian is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









asked yesterday









Jonathan MaximilianJonathan Maximilian

161




161




New contributor




Jonathan Maximilian is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.





New contributor





Jonathan Maximilian is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






Jonathan Maximilian is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











  • $begingroup$
    Maybe the implication is that if the husband's combination is unknown, it must mean that he does not have $aa$, since he would have shown symptoms already? Is the "(i.e., $AA, Aa, aa$)" yours, or the book's?
    $endgroup$
    – Brian Tung
    yesterday











  • $begingroup$
    mine, and your answer makes a lot of sense lol, but my assumption is correct if aa was included ?
    $endgroup$
    – Jonathan Maximilian
    yesterday










  • $begingroup$
    actually i rechecked, and the book doesnt say anything about the husband showing early symptoms, it just says that the probability a priori is what i wrote in my post (1/80)
    $endgroup$
    – Jonathan Maximilian
    yesterday










  • $begingroup$
    Yeah, I don't know. Is the book online by any chance?
    $endgroup$
    – Brian Tung
    yesterday










  • $begingroup$
    no and its not in english lol, do you know if my attempt is correct? can you just sum the two probability trees together?
    $endgroup$
    – Jonathan Maximilian
    yesterday
















  • $begingroup$
    Maybe the implication is that if the husband's combination is unknown, it must mean that he does not have $aa$, since he would have shown symptoms already? Is the "(i.e., $AA, Aa, aa$)" yours, or the book's?
    $endgroup$
    – Brian Tung
    yesterday











  • $begingroup$
    mine, and your answer makes a lot of sense lol, but my assumption is correct if aa was included ?
    $endgroup$
    – Jonathan Maximilian
    yesterday










  • $begingroup$
    actually i rechecked, and the book doesnt say anything about the husband showing early symptoms, it just says that the probability a priori is what i wrote in my post (1/80)
    $endgroup$
    – Jonathan Maximilian
    yesterday










  • $begingroup$
    Yeah, I don't know. Is the book online by any chance?
    $endgroup$
    – Brian Tung
    yesterday










  • $begingroup$
    no and its not in english lol, do you know if my attempt is correct? can you just sum the two probability trees together?
    $endgroup$
    – Jonathan Maximilian
    yesterday















$begingroup$
Maybe the implication is that if the husband's combination is unknown, it must mean that he does not have $aa$, since he would have shown symptoms already? Is the "(i.e., $AA, Aa, aa$)" yours, or the book's?
$endgroup$
– Brian Tung
yesterday





$begingroup$
Maybe the implication is that if the husband's combination is unknown, it must mean that he does not have $aa$, since he would have shown symptoms already? Is the "(i.e., $AA, Aa, aa$)" yours, or the book's?
$endgroup$
– Brian Tung
yesterday













$begingroup$
mine, and your answer makes a lot of sense lol, but my assumption is correct if aa was included ?
$endgroup$
– Jonathan Maximilian
yesterday




$begingroup$
mine, and your answer makes a lot of sense lol, but my assumption is correct if aa was included ?
$endgroup$
– Jonathan Maximilian
yesterday












$begingroup$
actually i rechecked, and the book doesnt say anything about the husband showing early symptoms, it just says that the probability a priori is what i wrote in my post (1/80)
$endgroup$
– Jonathan Maximilian
yesterday




$begingroup$
actually i rechecked, and the book doesnt say anything about the husband showing early symptoms, it just says that the probability a priori is what i wrote in my post (1/80)
$endgroup$
– Jonathan Maximilian
yesterday












$begingroup$
Yeah, I don't know. Is the book online by any chance?
$endgroup$
– Brian Tung
yesterday




$begingroup$
Yeah, I don't know. Is the book online by any chance?
$endgroup$
– Brian Tung
yesterday












$begingroup$
no and its not in english lol, do you know if my attempt is correct? can you just sum the two probability trees together?
$endgroup$
– Jonathan Maximilian
yesterday




$begingroup$
no and its not in english lol, do you know if my attempt is correct? can you just sum the two probability trees together?
$endgroup$
– Jonathan Maximilian
yesterday










1 Answer
1






active

oldest

votes


















1












$begingroup$

You have mentioned that the father could be AA, Aa, or aa. What we need to remember is that these represent the alleles he received from his parents. So, if we let the first letter represent the allele received from his father and the second letter represent the allele gained from his mother, there are actually four possibilities: AA, Aa, aA, aa. That is, the father has a 1/4 chance of being either AA or aa, but a 2/4 = 1/2 chance of being Aa.



When these are combined with the known Aa of the mother, you will see that there are 4 of 16 possibilities resulting in aa. Thus, the probability of being aa are 1/4 ... and if 1/20 of those have the disease, then the result is 1/80.






share|cite|improve this answer








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Den Zelle is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






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    $begingroup$

    You have mentioned that the father could be AA, Aa, or aa. What we need to remember is that these represent the alleles he received from his parents. So, if we let the first letter represent the allele received from his father and the second letter represent the allele gained from his mother, there are actually four possibilities: AA, Aa, aA, aa. That is, the father has a 1/4 chance of being either AA or aa, but a 2/4 = 1/2 chance of being Aa.



    When these are combined with the known Aa of the mother, you will see that there are 4 of 16 possibilities resulting in aa. Thus, the probability of being aa are 1/4 ... and if 1/20 of those have the disease, then the result is 1/80.






    share|cite|improve this answer








    New contributor




    Den Zelle is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
    Check out our Code of Conduct.






    $endgroup$

















      1












      $begingroup$

      You have mentioned that the father could be AA, Aa, or aa. What we need to remember is that these represent the alleles he received from his parents. So, if we let the first letter represent the allele received from his father and the second letter represent the allele gained from his mother, there are actually four possibilities: AA, Aa, aA, aa. That is, the father has a 1/4 chance of being either AA or aa, but a 2/4 = 1/2 chance of being Aa.



      When these are combined with the known Aa of the mother, you will see that there are 4 of 16 possibilities resulting in aa. Thus, the probability of being aa are 1/4 ... and if 1/20 of those have the disease, then the result is 1/80.






      share|cite|improve this answer








      New contributor




      Den Zelle is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






      $endgroup$















        1












        1








        1





        $begingroup$

        You have mentioned that the father could be AA, Aa, or aa. What we need to remember is that these represent the alleles he received from his parents. So, if we let the first letter represent the allele received from his father and the second letter represent the allele gained from his mother, there are actually four possibilities: AA, Aa, aA, aa. That is, the father has a 1/4 chance of being either AA or aa, but a 2/4 = 1/2 chance of being Aa.



        When these are combined with the known Aa of the mother, you will see that there are 4 of 16 possibilities resulting in aa. Thus, the probability of being aa are 1/4 ... and if 1/20 of those have the disease, then the result is 1/80.






        share|cite|improve this answer








        New contributor




        Den Zelle is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
        Check out our Code of Conduct.






        $endgroup$



        You have mentioned that the father could be AA, Aa, or aa. What we need to remember is that these represent the alleles he received from his parents. So, if we let the first letter represent the allele received from his father and the second letter represent the allele gained from his mother, there are actually four possibilities: AA, Aa, aA, aa. That is, the father has a 1/4 chance of being either AA or aa, but a 2/4 = 1/2 chance of being Aa.



        When these are combined with the known Aa of the mother, you will see that there are 4 of 16 possibilities resulting in aa. Thus, the probability of being aa are 1/4 ... and if 1/20 of those have the disease, then the result is 1/80.







        share|cite|improve this answer








        New contributor




        Den Zelle is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
        Check out our Code of Conduct.









        share|cite|improve this answer



        share|cite|improve this answer






        New contributor




        Den Zelle is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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        answered yesterday









        Den ZelleDen Zelle

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        113




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