Help with question

#1
The Food and Nutrition Board of National Acadamy of Sciences states that reccomended daily allowance (RDA) of iron for adult females under the age of 51 is 18mg. The board suspects that the actual amount of iron intake is less than the RDA of 18mg. Thus we want to test Ho: u=18 vs Ha: u<18 with a 5% level of signifigance based on a sample size of 20. Assume that the population standard deviation is 4.2mg.

a. What is the rule for rejecting Ho in terms of z?
b. What is the rule for rejecting Ho in terms of x-bar?

I'm not really sure what they are looking for, for an answer for these questions, can someone give me a hint as to what they are looking for?

Thanks
 
E

elnaz

Guest
#2
hello
Z(.05)<Zo iff reject H0 Zo=(((X-bar)obs-18)/(4.2/sqrt(20))

X-bar<k iff reject H0 and k is such that p(X-bar<k)=.95
X-bar~N(18,(4.2^2)/20)