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## How do you calculate standard deviation in SQL?

Generally, you should **use STDEV** when you have to estimate standard deviation based on a sample. But if you have entire column-data given as arguments, then use STDEVP . In general, if your data represents the entire population, use STDEVP ; otherwise, use STDEV .

## How does Hive calculate standard deviation?

Hi Lefty, The Hive aggregate functions as you provide just states: **DOUBLE stddev_pop(col) Returns the standard deviation** of a numeric column in the group. DOUBLE stddev_samp(col) Returns the unbiased sample standard deviation of a numeric column in the group.

## How do you do standard deviation?

**To calculate the standard deviation of those numbers:**

- Work out the Mean (the simple average of the numbers)
- Then for each number: subtract the Mean and square the result.
- Then work out the mean of those squared differences.
- Take the square root of that and we are done!

## What is Stddev_samp?

The STDDEV_SAMP and STDDEV_POP functions **return the sample and population standard deviation of a set of numeric values** (integer, decimal, or floating-point). The result of the STDDEV_SAMP function is equivalent to the square root of the sample variance of the same set of values.

## What is 2 standard deviations below the mean?

A score that is two Standard Deviations above the Mean is at or close to the 98th percentile (PR = 98). A score that is two Standard Deviations below the Mean is **at or close to the 2nd percentile (PR =2)**. … On most psychological and educational tests, the mean is 100 and the Standard Deviation is 15 points.

## What is a good standard deviation?

Statisticians have determined that values no greater than plus or minus 2 SD represent measurements that are more closely near the true value than those that fall in the area greater than **± 2SD**. Thus, most QC programs call for action should data routinely fall outside of the ±2SD range.

## Where is standard deviation used?

The standard deviation is used **in conjunction with the mean to summarise continuous data**, not categorical data. In addition, the standard deviation, like the mean, is normally only appropriate when the continuous data is not significantly skewed or has outliers.