Statistics: Confidence Intervals

[jlo2006]

Heres the problem:

Mr. K would like to know what percentage of the senior class has watched the movie Groundhog Day. He would like to be sure to within 0.05 or 5%. He wants to compute a 90% confidence interval. How many students must he poll in order to achieve these goals?

Help Please. Greatly Appreciated.

 

[EnumaElish]

See Confidence intervals for proportions and related quantities

and generally Confidence interval