Yes, thank you very much for your answer, it helped me to remove this doubt, in the books I took to study there was no such explanation and I was always confused. Thank you very muchYou haven't given the whole question, so I'm assuming you are given n=25.
When p-hat=0.75, z=(0.75 - 0.80)/0.08 = -0.625 (Note that sqrt(0.0064)=0.08)
If you draw a diagram the probability you want is the part shaded under the normal curve to the left of x=-0.625.
This is 0.2660 approx. (Bit different to your answer because I use the exact value of -0.625 rather than -0.63)
I should have said ..."to the left of z=-0.625". ( ie z not x)Yes, thank you very much for your answer, it helped me to remove this doubt, in the books I took to study there was no such explanation and I was always confused. Thank you very much