# I am trying to figure out the stationarity of time series data

Here, this plot shows the number of customers served per day from 1 jan 2018 to 31 dec 2019.

I grouped the entire data by each month and calculated the average and variance per month.

This is the average

This is the variance

I also ran an augmented dickey-fuller test and got the following result

ADF Statistic: -26.031963

p-value: 0.000000


Since, the mean and variance do not vary too much, should I infer that the data is stationary?

On the other hand I would be concerned with your test results. Getting a p of exactly zero, and a test statistic value of way below -3 or -4 I would look at your implementation again and check if it's right.