April 2013 Question 8 part iia)

Discussion in 'CS1' started by Molly, Mar 22, 2023.

  1. Molly

    Molly Ton up Member

    Hi all,

    in the confidence interval, they seem to take the residual of MSS to be the combined variance. Please could someone explain why this is the case?

    Thanks

    Edit: Also, even if MssRes does equal sample variance (im not sure why this is), then doesnt MSS res include sample C too even though we just want a CI for A and B?
     
    Last edited: Mar 22, 2023
    Molly, Mar 22, 2023
    #1
  2. Andrea Goude

    Andrea Goude ActEd Tutor Staff Member

    Hi Molly
    MSS_RES=SS_RES/(n-k-1)=sigma_hat^2
    Yes sigma_hat^2 would include sample C, but you don't have the information on just A and B, so ii)b) is acknowledging that C is causing the significant result in i).
    Thanks
    Andrea
     
    Andrea Goude, Mar 22, 2023
    #2
    Molly likes this.
  3. Molly

    Molly Ton up Member

    ah thats great thank you !
     
    Molly, Mar 22, 2023
    #3

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