Standard Deviation and Variance

Prob. and Stats

Difficulty: 1 | Problem written by Mr. Umair
Problem reported in interviews at


The Standard Deviation is a measure of how spread out numbers are. In statistical analysis, standard deviation plays an important role. It can be computed using below given formula.

                                                        \(\sigma =\sqrt{\frac{1}{N}\sum_{i=1}^{N}(X_i-\mu)^2}\)


Variance can be defined as the average of the squared differences from the Mean. It can be calculated using below given formula.

                                                        \(\sigma^2 =\frac{1}{N}\sum_{i=1}^{N}(X_i-\mu)^2\)



Our function will take 1D NumPy Array and computes standard deviation and variance using array given in input.


This function will return a list having length 2 which contains Standard Deviation and Variance in their corresponding place.

Sample Input:
<class 'list'>
arr: [array([8, 8, 3, 7, 7, 0, 4])]

Expected Output:
<class 'list'>
[2.813959371941744, 7.918367346938775]

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Input Test Case

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numpy has been already imported as np (import numpy as np)