Find the minimum sample size needed to estimate the percentage of Democrats who have a sibling. Use a 0.1 margin of error, use a confidence level of 98%, and use the results from a prior Harris poll that gave a confidence interval of (0.44, 0.51) for the proportion of Democrats who have a sibling.

Respuesta :

Answer:

The minimum sample size is  [tex]n =135[/tex]

Step-by-step explanation:

From the question we are told that

   The confidence interval is [tex]( lower \ limit = \ 0.44,\ \ \ upper \ limit = \ 0.51)[/tex]

    The margin of error is  [tex]E = 0.1[/tex]

   

Generally the sample  proportion can be mathematically evaluated as

     [tex]\r p = \frac{ upper \ limit + lower \ limit }{2}[/tex]

    [tex]\r p = \frac{ 0.51 + 0.44}{2}[/tex]

    [tex]\r p = 0.475[/tex]

Given that the confidence level is  98% then the level of significance can be mathematically evaluated as

         [tex]\alpha = 100 - 98[/tex]

        [tex]\alpha = 2\%[/tex]

        [tex]\alpha =0.02[/tex]

Next we obtain the critical value of  [tex]\frac{\alpha }{2}[/tex] from the normal distribution table  

   The value is

        [tex]Z_{\frac{\alpha }{2} } = 2.33[/tex]

Generally the minimum sample size is evaluated as

      [tex]n =[ \frac { Z_{\frac{\alpha }{2} }}{E} ]^2 * \r p (1- \r p )[/tex]

     [tex]n =[ \frac { 2.33}{0.1} ]^2 * 0.475(1- 0.475 )[/tex]

     [tex]n =135[/tex]