Ch 14 "observing a single value of x" and "given x"

Discussion in 'CS1' started by Molly, Feb 24, 2023.

  1. Molly

    Molly Ton up Member

    Hi all,

    i understand when the question states "observing a single value of x" we do not need to do the product of the likelihood function. But in question 4 it doesnt specify that we only have one value of x, and it says "yields x successes", so i would have thought that we would be thinking of more than one value of x here. However the answers should the likelihood function to be
    p^x (1-p)^(n-x) where as i would have thought it would be p^\sumx_i (1-p)^(n-\sumx_i)

    Is there a reason for this? is there an easy way i can tell when we need to find the product and when we dont?

    Thanks
     
  2. CapitalActuary

    CapitalActuary Ton up Member

    I have no idea what you’re referring to as I don’t have any of the notes, but it sounds like perhaps x in the course notes is referring to the sum of b_i where b_i is 1 if a success or 0 otherwise. i.e. each b term is an observation of an individual success or failure, but the x is the observation of the total number of successes.

    Whereas you are using each x_i like I am using b_i above.

    Sounds to me like a difference in notation, without knowing more.
     
    Andrea Goude and Molly like this.
  3. Molly

    Molly Ton up Member

    ah that does make sense thank you, so definitely something to look out for when using the binomial distributions!
     

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