Question

A newspaper article estimated that the mean cost for preventive dental care was $165 per year. They indicated that the estimate was based on a sample of 100 people and that the margin of error was 2.8. Assuming a 95% confidence level was used, calculate the value of the standard error.

Answer 1

a=0.05, |Z(0.025)|=1.96 (check standard normal table)

Margin of error$=Z\times standard \;error = 2.8$

--> $1.96\times standard \; error= 2.8$

So Standard error = $\frac{2.8}{1.96}=1.428571$