Margin of error
The margin of error is a statistic expressing the amount of random sampling error in a survey's results. The larger the margin of error, the less confidence one should have that the poll's reported results are close to the "true" figures; that is, the figures for the whole population. Margin of error is positive whenever a population is incompletely sampled and the outcome measure has positive variance (that is, it varies).
Formula of margin of error of population means
\[+z*\frac{k}{\sqrt{n}}\] or
\[-z*\frac{k}{\sqrt{n}}\]
here Z is score ,k is standard deviationand n is sample size
Boundary conditions
1.Random variable X should be Normal
2. k should be known
3. n must be greater than equal to 30
Example- for z=1.645 Standard deviation k=0.5 and n =40 we get 0.13
