I have the normalized wavefunction u(x)=1/sqrt(L) when -L/2 < x < L/2 and zero everywhere else. I want the value of p when the probability of getting a measurement result close to p i maximal/minimal. I seek for maximum/minimum probability density! I was thinking of Fouriertransform u(x) to get y(p). Then take |y(p)|^2 -- that is the probability distribution in p-space isnt it? Then take d/dp(|y(p)|^2) and get the maxima and the minima of the function. The thing is that in this way i get a strange expression for the derivate and i dont find the maxima and the minima like i want! I can´t evaluate the expression i get! Can anyone help me in this way or in another way please!?