A Gallup poll reported that 58% of Americans say they are satisfied with the costs of healthcare. If the margin of error was 1.5%, approximately what was the sample size?

Respuesta :

we can use the following formula for the margin of error:

[tex]ME=1.96\sqrt[]{\frac{p(1-p)}{n}}[/tex]

where p is the proportion and n the sample size

p = 58% = 0.58

ME = 1.5% = 0.015

therefore:

[tex]0.015=1.96\sqrt[]{\frac{0.58(1-0.58)}{n}}[/tex]

now, we need to solve for n

[tex]\begin{gathered} \frac{0.015}{1.96}=\sqrt[]{\frac{0.58(1-0.58)}{n}} \\ \frac{0.58(1-0.58)}{n}=(\frac{0.015}{1.96})^2 \\ 0.58(1-0.58)=n\cdot(\frac{0.015}{1.96})^2 \\ 0.58\cdot\: 0.42=n\cdot0.00765^2 \\ n=\frac{0.58\cdot0.42}{0.00765^2}=4159.17226 \end{gathered}[/tex]