SOLUTION: The marks on statisties midierm test are normally distobuted witha mean of 78 and a slandard deviation of 6. (a) What proportion of the elass has a midierm ntark ot less than 75? (

Algebra ->  Probability-and-statistics -> SOLUTION: The marks on statisties midierm test are normally distobuted witha mean of 78 and a slandard deviation of 6. (a) What proportion of the elass has a midierm ntark ot less than 75? (      Log On


   



Question 1157930: The marks on statisties midierm test are normally distobuted witha mean of 78 and a slandard deviation of 6. (a) What proportion of the elass has a midierm ntark ot less than 75? (B) What is the probabilily that class of 50 has an average midterm mark that is less than 75?
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
z=(x-mean)/sd
for a z <-1/2 and that probability is 0.3085
z=(x bar-mean)/sigma/sqrt(n)
here, z< (-3)*sqrt(50)/6 or -3.54 and that probability is 0.0002
Far less likely for the whole class to get below 75.