Sorry I am not scientific but I thought the mean was 0…! In fact I just want to know how to interpret -1 to +1 in order to find the highest amplitude?

# Access alpha_relative value from Muse Headband

**Enigma644**#22

Mean is another way of saying average, or expected value.

I’m not sure what you mean by trying to find the highest?.. the highest number is the highest number! In one data set this might be 1, in another it might be 0.2, or 3. It depends what you have recorded!

**Walid**#23

I mean the highest number of the five different brain waves when compared at a time t, in realtime.

**Anthony**#25

I’m measuring the largest value for a given absolute value as 1.84 and the smallest as -1.57, I thought that these values could only range between 1 and -1, perhaps it’s 2 and -2? Thanks

**Enigma644**#26

There is no set range. I’ve only said in the past that the *usual* range is around [-1:+1], but I regularly see [+5:-5] in recordings and there’s no reason it couldn’t extend beyond that.

**Anthony**#27

Okay that’s interesting, I’m just learning now that FFT is a broad signal analysis algorithm and has nothing to do with EEG in particular. What value is there in calculating a PSD for a given frequency? Thanks for the help with this

**Enigma644**#28

Calculating each frequency gives you a more granular view (than for example regular “Alpha” which is for everything in 7.5Hz to 13Hz). As to why you’d need that, it would depend on your research. I imagine noise isolation for certain frequencies would be one good reason.

**Anthony**#29

So as long as I use the absolute value for each wavelength type (alpha etc) I should be OK?