the mean and std value of a standard normal distribution

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yue li 2018-8-28

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评论： yue li 2018-8-28

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Hello,

I used matlab example https://www.mathworks.com/help/stats/normal-distribution.html

Compute the pdf of a standard normal distribution, with parameters µ equal to 0 and σ equal to 1. The mean value of norm should be 0, and the std value of norm should be 1.

Why the mean value of norm is 0.1636, and the std value is 0.1408?

Thanks in advance!

Yue

    x = [-3:.1:3];
    norm = normpdf(x,0,1);
    >> norm_mean=mean(norm)
    norm_mean =
    0.1636
    >> norm_std=std(norm)
    norm_std =
    0.1408

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Adam 2018-8-28

You are taking the mean and std of the values on the y axis of the pdf, not the x axis, which is a fairly meaningless statistic.

yue li 2018-8-28

编辑：yue li 2018-8-28

Hello, Adam,

Thank you so much for your great help!

Yue

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Image Analyst 2018-8-28

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norm() is a built-in function so don't use that for your variable name.

Try using randn() and then using mean() and std() on that.

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yue li 2018-8-28

Hello, Image Analyst,

Thank you do much for your reminding!

Yue

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