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? (

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) (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.
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