I was wondering if I am even answering these questions right.

The Better Business Bureau has several complaints that a flour company is under-filling their 5 pound flour bags. The Bureau randomly selects 750 bags of flour and determines the weight of each bag. The sample average of the bags is 4.80 pounds with a standard deviation of .15 pounds. Is there overwhelming evidence at the .01 level that the bags are under-filled?

M = 5

x = 4.8

n = 750

s = .15

z = (x-M)/(s/n^(1/2))

z = (4.8-5)/(.15/750^(1/2))

= -36.5

The next step I am unsure of.

P = P(z>-36.5) < .005?

How do I get the z value? I have a table in the back of the book that only shows up to -3.4 but that is .0003 so -36.5 has to be much less then that so it is true? Not even sure I am doing this right.

A fuel oil company claims that one-fifth of the homes in a certain city are heated by oil. Do we have reason to doubt this claim if, in a random sample of 1000 homes in this city, it is found that 136 are heated by oil? Use a .01 level of significance.

p = .20

q = .8

n = 1000

x = 136

z = (x-np)/(npq)^(1/2)

z = (136-1000(.2))/(1000*.2*.8)^(1/2)

= -5.06

P = P(z > -5.06) < .005

The oil company is right?

Again not sure I am using right formula or doing it right. Also q is just 1-p, correct?

Thanks