Normally distributed values

Is there a way in excel to check whether particular values are normally distributed (and thus follow the normal distribution function) or not?

What about the values below? Are they normally distributed?
marks



Thank you for the help,

Best

Jamal

Hi Jamal
Have a look at this link.
http://academy.excelhero.com/vanilla...uted-values/p1
Hope it helps.
Tony

Many thanks for the answer OTPM.

I couldn’t find an answer for my issue in the link that you have already provided.

My question is simple: how check whether particular values are normally distributed or not?

Is there a tool on the Excel which can do this sort of work straight forward?

Best

Jamal

Hi Jamal

Have you tried NORM.S.DIST()?

Tony

Many thanks for the prompt answer

I feel that my question is still not answered. For example, suppose that we have the values below:


Then how to check whether they are normally distributed or not?
How to apply the function “NORM.S.DIST()” in this case?

Best

Jamal

Attached Images

Clip_86.jpg (86.5 KB, 12 views)

Hi Jamal
Your question is probably a little beyond me. However have a look at this link which MAY help you:

http://www.oup.com/uk/orc/bin/978019...ox5-2excel.pdf

Good luck
Tony

Many thanks for the help. The link you have provided sounds to be very useful. I’ll try it and see it may solve my issue.

Appreciated

Jamal

Hi Jamal,

It's not clear exactly what you want. If you're trying to find out whether the data approximates a normal distribution, the first step would be to graph them. To set up the graph, you could use a formula like:
=8.74-ABS(AVERAGE(A$2:A$20)-A2)
The '8.74' is just to 'normalise' the balance of the formula to a (rough) zero base

As you'll see, your data don't bear much resemblance to a normal distribution. However, how much variation from a normal distribution is allowed is a matter of judgement.

FWIW, a normal distribution would be much closer to:
70
70.25
71.25
72.25
73.5
75
76.5
77.5
78.25
78.5
78.75
79.5
80.5
82
83.5
84.75
85.75
86.75
87

Cheers

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]

Hi Paul,

Thak you for the answer.

This is exactly what I’m looking for. Given a set of data (assume that they are students marks), and it is first needed to check (in principle) if they are normally distributed (or follow the normal distribution function).

I couldn’t find “direct” tool in the Excel that do this sort of work.

Could you please elaborate more regarding the method that you have used to check whether the “marks” are normally distributed and namely the equation?

=8.74-ABS(AVERAGE(A$2:A$20)-A2)

What does 8.74 represent?





Is this related to normalosing values by their max and min values

Xnew=Xold-Xmin/Xmax-Xmin

Or by their average and standard deviation

Xnew=Xold-avrage/standard deviation


Best

Jamal

Attached Images

Clip_18.jpg (91.5 KB, 11 views)

Attached Files

Book1.xlsx (13.2 KB, 8 views)

As indicated in my previous post:
It has no other significance.

The figures I posted were not those of an actual normal distribution curve - they were just my manual approximation of what one might look like for data spanning the number range you posted. The actual curve might be flatter or steeper than my figures suggest. In any event, for so few results, it would be unreasonable to expect a close approximation of the true normal distribution curve. You might need a few hundred results before you would have a really close approximation of the true normal distribution curve - it all depends on how variable the data are. For example, to attain 90% confidence that your sample data are within 5% of a normal distribution, you'd need a minimum sample size of 271. 95% confidence would require a minimum sample size of 385.

If you need to analyse the data statistically, you'll need some understanding of the theory. You should perhaps get a copy of Freund's Modern Elementary Statisics. See also:
http://en.wikipedia.org/wiki/Normal_distribution
http://en.wikipedia.org/wiki/Sample_size

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]

Many thanks Paul for the answer.

I thought there might be a simple tool that can check a set of data whether they are normally distributed or not.

I think that I have sufficient background regarding this topic. My issue is that to use the normal distribution function (attached), it is required first to check whether the data is normally distributed. I attempt to find a tool that does this sort of work but sounds that this a bit confusing.

In other words, having normally distributed data is a condition to apply the normal distribution function for further analysis! But how can we first check our raw data (whether it is normally distributed or not?!)

Best

Jamal

Attached Images

Clip_22.jpg (12.8 KB, 11 views)

As in all statistics there is no simple yes/no answer. All you can establish is a degree of probability about the numbers obtained being normally distributed within certain limits.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]

many thanks Paul.

best

Jamal