From a population with a variance of 900, a sample of 225 items is selected. At 95% confidence, the margin of error is 3.92.
The margin of error is a statistic expressing the amount of random sampling error in the results of a survey. The larger the margin of error, the less confidence one should have that a poll result would reflect the result of a census of the entire population. The margin of error will be positive whenever a population is incompletely sampled and the outcome measure has positive variance, which is to say, the measure varies.
Margin of error at alpha level of significance =
Z score at alpha level of significance * sqrt(variance/ sample size)
Z score at 5% level of significance = 1.96
Variance = 900
Sample size = 225
Margin of error = [tex]1.96 *\sqrt{\frac{900}{225} } = 1.96*\frac{30}{15} = 3.92[/tex]
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