Frequently Asked Questions

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What is the difference in the formulas of variance and standard deviation?


The formula of the variance is the average of the squared deviations from the mean while the formula of standard deviation is the square root of a number (variance result).

How variability can be measured?


Variability can be measured in four different ways

  • Range: Difference between highest and lowest value.
  • Interquartile range: the range between the middle half of the distribution.
  • Standard deviation: Typical distance of data values from the mean.
  • Variance: Average of squared distances from the expected value.

How to find the standard deviation?


To calculate the standard deviation follow the below steps.

Step 1: Calculate the mean.

Step 2: Find the difference between each data value from the mean.

Step 3: Take the square of deviations to make them positive.

Step 4: Add the squared deviations.

Step 5: Divide the square deviations by the degree of freedom (n-1) or (n).

Step 6: Take the square root of the result of the quotient. The result will be a standard deviation.

Why standard deviation is used?


A standard deviation measures how variable your data set is on average. The average deviation from the mean gives you the distance between each observation and the mean.