Math Is Fun Forum

David

Member

From: Bumpkinland

Registered: 2014-04-23

Posts: 3,164

Standard Deviation?

Hi;
From my friend :
Hello everyone, I would like to ask you something about calculating mean and standard deviation. I am trying to calculate the standard deviation for my data, I am using the likert scale with 4 points. so i already know how to count mean but I'm a little confused with standard deviation.

What should I do? At the moment I'm not not sure if my data is grouped or ungrouped.
My data is like this :

1234 at the column
And each row is the questions
Let's take question 4
1×1 + 2×3 + 3×18 + 4×8
The total I'll get the mean
But now with that how do I find the standard deviation?

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His dominion is an everlasting dominion, Which shall not pass away, And His kingdom the one Which shall not be destroyed.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Standard Deviation?

Hi;

I do not know anything about the likert scale. How does this apply?

http://www.measuringusability.com/blog/ … ponses.php

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,621

Re: Standard Deviation?

hi chooipian

I have doubts about the wisdom of doing any statistics without knowing the survey questions.  A Likert scale is a multi-choice type survey like this:

Q1 I like MathisFunForum.  (1) strongly disagree (2) disagree (3) agree (4) strongly agree.

Converting responses into equal interval numbers is fraught with bias, but, ok, I'll go with it for now.

In calculating the mean answer you are, in effect, treating the responses as 'weights' and using the mean for grouped data formula:

So the corresponding formula for variance would be:

But what will you do with these statistics ?

Hope that helps. 

Bob

Last edited by Bob (2014-08-09 06:08:42)

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob