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Updated on: 19 Aug 2020, 07:13
Originally posted by sahilaro23 on 15 Aug 2020, 06:29.
Last edited by sahilaro23 on 19 Aug 2020, 07:13, edited 1 time in total.
Last edited by sahilaro23 on 19 Aug 2020, 07:13, edited 1 time in total.
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How to calculate Standard Deviation - The easy way
Given set is - (1,2,3,4,5)
Step 1 Take mean of (1,2,3,4,5) = (1+2+3+4+5)/5
Mean = 3
Step 2 subtract mean from each element.
(3-1, 3-2, 3-3, 3-4, 3-5)
(2,1,0,-1,-2)
Step 3
Add the Squares of these elements and take mean again
= (4+1+0+1+4) = 10/5 = 2
Step 4:
Take root of step 3= SD = √2.
Happy Learning
Given set is - (1,2,3,4,5)
Step 1 Take mean of (1,2,3,4,5) = (1+2+3+4+5)/5
Mean = 3
Step 2 subtract mean from each element.
(3-1, 3-2, 3-3, 3-4, 3-5)
(2,1,0,-1,-2)
Step 3
Add the Squares of these elements and take mean again
= (4+1+0+1+4) = 10/5 = 2
Step 4:
Take root of step 3= SD = √2.
Happy Learning
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19 Aug 2020, 07:10
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sahilaro23
This is not correct. That's easy to see using just a two-element set; the standard deviation of {10, 20}, for example, is 5, because every value is 5 away from the mean. It is not, as your formula would suggest, equal to 10√2. Or, if you take one of the very rare larger sets with an integer standard deviation, a list of seven consecutive integers:
1, 2, 3, 4, 5, 6, 7
that list famously has a standard deviation of 2, and not, as your formula would suggest, of √2. Your formula is producing the right answer for the specific set you provide, but will not produce the correct answer for smaller or larger sets.
But you definitely do not need to calculate standard deviations on the GMAT.
Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
