Given a normal distribution with mean = 82 and standard deviation = 25 , Find the probability that X assumes a value ?
A. Less than 78 = (Correct Answer: 0.2119) (My Answer : 0.4364)
Why the hell im wrong I convert the value of X to Z using x-mean/standard deviation = -0.16 which is the value of 0.4364 in Z table
Indeed $$ \Phi \left(\frac{78-82}{25} \right) = \Phi(-0.16) \approx 0.4364 $$ but $$ \Phi \left(\frac{78-82}{\sqrt{25}} \right) = \Phi(-0.8) \approx 0.2119 $$ Maybe the variance and standard deviation got mixed up.