I'm trying to do an error analysis and I was asked to calculate the confidence intervals but was told that I need to calculate the true number of statistically independent samples for doing this. I am not very familiar with statistics whatsoever and really have no idea what I'm supposed to do.
I was told to find the autocorrelation and then determine how far I'll count the data before deciding the data isn't correlated anymore. The data is 40960 samples (a sampling frequency of 4096 Hz for ten seconds) of voltages measured on a load cell in a wind tunnel.
So I did some research and am using the autocorr function on matlab but still don't understand a few things:
1) How many lags I should use?
2) How to use the data from autocorr to find the # of independent samples?
I've included a picture of what Matlab displays after using the autocorr function. The default lag number of the function is 20.