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Confidance interval on contingency table

  • 21-09-2004 2:06pm
    #1
    Xterminator
    Registered Users, Registered Users 2 Posts: 4,782 ✭✭✭


    Hi,

    I'm not sure hoe to get started on this assigment question.

    I have a contingency table,, where a sample of 330 from unknown total were asked a question, with possible replies yes/no/undecided . The total for no is 46. But no st deviance is given

    I need to calcualte a 90% confidance interval, which ithe formula is
    x bar +or- z value * (sigma/root n)

    Putting in the variables, 46+or-1.645 (z at 90%) * st dev/ root 330 .
    But as i dont know st dev, so i cant finish the first part of question.

    but as i dont have st deviation ... what do i do? any ideas please.


Comments

  • #2
    denachoman
    Registered Users, Registered Users 2 Posts: 173 ✭✭denachoman


    Bit rusty so this may be way off the mark

    If you assume binomial where p = yes
    and q = no or undecided then
    std dev = root of npq = root of [330*(46/330)*(284/330)] = 39.59

    CI = 46 +/- 1.645[39.59/root(330)]

    CI = [42.42, 49.58]


  • #3
    Xterminator
    Registered Users, Registered Users 2 Posts: 4,782 ✭✭✭Xterminator


    thks

    I hope ur right!

    X


  • #4
    Bradser
    Closed Accounts Posts: 2 ✭Bradser


    denachoman wrote:
    Bit rusty so this may be way off the mark

    If you assume binomial where p = yes
    and q = no or undecided then
    std dev = root of npq = root of [330*(46/330)*(284/330)] = 39.59

    CI = 46 +/- 1.645[39.59/root(330)]

    CI = [42.42, 49.58]


    thats incorrect.
    its a simple population porportion question.
    the formula given gives all the data that is required to do the question.
    i will do up a demonstration of how to tackle this problem and post it ASAP.


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