build a normal distribution graph based on small sample size

[yxz152830]

Gurus,
if I have a sample size of only 20. Is it viable to get the mean/sd based on the sample using excel under the assumption that the population is normally distributed?
If that's viable, what formula do I use?
I assume that in order to create a histogram of normal distribution, I would need a data set that's large enough to make interval small enough in order to create a smooth normal distribution graph. How do I generate the random data points using excel? Thank you!

 

[BigBeachBananas]

Gurus,
if I have a sample size of only 20. Is it viable to get the mean/sd based on the sample using excel under the assumption that the population is normally distributed?
If that's viable, what formula do I use?
I assume that in order to create a histogram of normal distribution, I would need a data set that's large enough to make interval small enough in order to create a smooth normal distribution graph. How do I generate the random data points using excel? Thank you!

The typical rule of thumb is to use the normal distribution when you have n>=30. The size of n=20 is considerably small, I would recommend using the t-distribution instead. As the sample size increases, the t-distribution becomes more similar to a normal distribution.

 

[JGordon11]

To get random numbers from a normal distribution use Norm.Inv(Rand(),µ,σ) where µ and σ are the mean and standard deviation respectively.

Similarly, to get random numbers from a t distribution T.Inv(Rand(),dof) where dof is degrees of freedom in your case n-1 = 19.

 

[AhoyNC]

The attached two links will show you how to build a normal distribution graph with your data. You would need to make decision if your data real fits a normal distribution or not.

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