Margin of Error calculation

[snix]

I am trying to calculate a margin of error. For example:

Same coin is flipped in the same way 15,000 (cell A2) times. 12,000 (cell
A1) times it ends heads up.

The formula I have created is:
=SQRT((A1/A2)*(1-A1/A2)/A2)

Is this correct?

Many thanks

snix.

 

[Jerry W. Lewis]

Your formula calculates the standard deviation of the estimated
proportion of heads. The most common definition of "margin of error"
www.amstat.org/sections/srms/brochures/margin.pdf
would be twice that.

Jerry
Excel MVP