What variance threshold to consider in feature selection?

Question

Consider a numerical dataset with continuous variables, that has been scaled to end up with values in the [0,1] range. How can I compute a reasonable variance threshold for all the variables?

Answer 1

Usually 3 is taken as a threshold Value by standard deviation

Using z-score we can look for value above or below threshold like in code below:

threshold=3
mean = np.mean(data)
std =np.std(data)

for x in data:
    z_score= (x - mean)/std 
    if np.abs(z_score) > threshold:
        ...