Image of confidence interval at 95% level

Margin of Error


The margin of error indicates the level of random sampling error generated by drawing a sample as opposed to conducting a census. It is expressed as + or – of the statistic and falls as the sample size rises (it’s highest at 50%)..

It can be calculated by multiplying the critical value by either the standard deviation or the standard error of the statistic. P is the percentage that the sample is seeking to measure (e.g. conversion rate of 6%).

Image of Margin of Error formulas



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