Originally Posted by

**kenshinofkin** [snip]

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? Mr F says: Yes.

Thanks