Find the probability of obtaining 25 samples with a mean height ranging from 60 to 63 inches from a normal population with a mean of 61 and a standard deviation of 5 inches?

Question

anonymous · Answer

z = (X-Mean) / (SD/sqrt n) 
z1 = (60-61) / 5/sqrt 25 = - 1 
z2 = (63-61) / (5/sqrt 25) = + 2 
The area under the standard normal curve between these two z values indicates the required probability. 
Required probability = P(60 < Xbar < 63) 
= P(- 1 < z < 2) 
= 0.3413 (area corresponding to z1 being -ve lies on the left side of mean) + 0.4772 (area corresponding to z2 being +ve lies on the right side of mean) 
Is the answer 0.8185 ?

welshfella · Answer

I think so. But its been a long time..   I'll look something up.

nincompoop · Answer

yes

nincompoop · Answer

do you have your z-table values?

anonymous · Answer

the answer is correct? yay. Thankyouuu yeap. But I'm just confirming

anonymous · Answer

stat is really hard

welshfella · Answer

yes - i just looked up some old notes.

Stats never came easy to me also.