# Standard Error

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## Definition of 'Standard Error'

In statistics, the standard error is a measure of how much random variation or error there is in a set of data. It is calculated by taking the square root of the variance. The variance is a measure of how far each data point is from the mean (average) of the data set.

The standard error is important because it tells us how much we can trust the results of a statistical analysis. If the standard error is small, then we can be more confident that the results are accurate. If the standard error is large, then we need to be more cautious about the results.

The standard error is often used in hypothesis testing. In hypothesis testing, we are trying to determine whether there is a statistically significant difference between two groups of data. The standard error is used to calculate the p-value, which is a measure of the probability that the difference between the two groups is due to chance.

The standard error can also be used to calculate confidence intervals. A confidence interval is a range of values that is likely to contain the true value of the population parameter. The width of the confidence interval is determined by the standard error.

The standard error is a useful tool for understanding the uncertainty in statistical data. It can be used to make informed decisions about the reliability of the results of a statistical analysis.

Here are some additional examples of how the standard error is used in statistics:

* The standard error is used to calculate the margin of error in a poll. The margin of error is the range of values within which the true value of the population parameter is likely to fall.
* The standard error is used to calculate the power of a statistical test. The power of a test is the probability of rejecting the null hypothesis when it is false.
* The standard error is used to calculate the sample size needed for a study. The sample size is the number of observations that are needed to achieve a desired level of precision.

The standard error is a fundamental concept in statistics. It is used to measure the uncertainty in statistical data and to make informed decisions about the reliability of the results of a statistical analysis.

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