Question

A political analyst found that 43% of 300 randomly selected Republican voters feel that the federal government has too much power. Find the 95%confidence interval of the population proportion of Republican voters who feel this way.

Answer 1

Find the 95% confidence interval of the population proportion of reputation of republic voters who feel this way using Excel-MegaStat:

From the given information, in the random sample of 300 republican voters, 43% feel that federal government has too much power. The confidence level is 95%.

The 95% confidence interval using Excel-MegaStat is,

 

Excel add-in (MegaStat)\r\nprocedure:

Step 1: In EXCEL, Select Add-Ins > MegaStat > Confidence intervals/Sample size.

Step 2: Choose Confidence intervals-p.

Step 3: Enter 0.43 as the p, and 300 as the n.

Step 4: In Confidence Level, Choose 95%.

Step 5: Click Preview and then OK.

 

MINITAB output:

Confidence interval – proportion

  95% confidence level

  0.43 proportion

   300 n

1.960 z

0.056 half-width

0.486 upper confidence limit

0.374 lower confidence limit

 

From the Excel-MegaStat output, the 95% confidence interval for the true proportion is (0.374, 0.486).

Thus, the 95% confidence interval of the population proportion of reputation of republic voters who feel this way is 0.374 < p < 0.486.

 

Interpretation:

There is 90% confident that true proportion of reputation of republic voters who feel this way lies between 0.374 and 0.486.

There is 90% confident that true proportion of reputation of republic voters who feel this way lies between 0.374 and 0.486.