Introduction to Statistics using NumPy

The formula you give for variance is the sample variance, with N - 1 as the divisor. It gives an unbiased estimate of the variance of a population, assuming X is a sample of that much larger population.

However, by default numpy gives you population variance, with N as the divisor. This assumes X is the entire population, which is different from R and Matlab.

As a result, the answer in your code is different from the formula just above it.

  np.var(X)

gives 207, while

  np.sum((np.array(X) - np.mean(X))**2) / (len(X) - 1)

gives 236. If you want the N-1 corrected sample variance from numpy you'd use

  np.var(X, ddof=1)

The problem with these kind of extremely short texts is that they jump into explaining technical concepts without even mentioning basic things such as random variable for example.

Then, readers learn that statistics is about applying a few summing and averaging procedures, and trust the numbers they get as a result.

Calculating mean, median, and average in Numpy. How is this in the first page of hacker news?

For such basic functionality, is there any reason not to just use Python 3's `statistics` module?

  from statistics import mean, median, stdev, variance

It's a little bit confusing that the article defines variance as "the averaged squared deviation of each data from your dataset" but then the formula shown is the unbiased estimation of the variance (with n-1 in the denominator) without explanation.

Nice example. But two typos,

Missing a close paren to open(); and splitlines() is misspelled. Code should be:

with open('salary.txt') as f: X = f.read().splitlines()

Where did you get the dataset from? Adding a link to the source would be nice

Nice, thanks! One question: where do you have the dataset from? The gender is encoded as 0,1,2 - which is which? Is this dataset from the Excel that was posted here some time ago? Could you share the link please?

I started to look at the dataset a little, if someone is interested: https://github.com/davidgengenbach/developer-salary-statisti...