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    Confidence interval for the difference of proportions

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    Please help with the following problem. Provide step by step calculations.

    After a certain candidate announced his intention for running for the premiership of a province, many polls were conducted to assess his chanced for success. Among them were two polls of independant samples taken from two populations. The poll in the first community interviewed 400 people and asked if the candidate had a chance of becoming the next premier. Out of this sample of 400, 192 people responded "yes". In the second community, 300 people were asked exactly the same question, and 108 answered "yes".
    Develop a 90% confidence interval for the difference of proportions who answered "yes".

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    Solution Preview

    First population
    p1= 0.48 =192/400 =proportion of those who say yes
    q1=1-p= 0.52 = 1 - 0.48 =proportion of those who did not say yes
    n1= 400

    Second population
    p2= 0.36 =108/300 =proportion of those who say yes
    q2=1-p= 0.64 = 1 - 0.36 ...

    Solution Summary

    Confidence interval for the difference of proportions is calculated in this solution.