# Homework Help: Analysis necessary to reduce the concentration of PCBs

1. Jul 5, 2010

### jingjang

Hello

i have a problem with my homework and i hope someone can help me? because i really dont know how to calculate this
so its translated with google translate

Major customer PCB (polychlorinated biphenyls, a hazardous substance used in
manufacture of transformers and capacitors), bring in small quantities PCBja
wastewater environment. Permissible concentration in water PCBja standard 5ppm
(Parts per million). Factory Administration issued internal instructions that must be stopped
production if the average concentration in the effluent PCBja exceed 3 ppm. Analysis
effluent in 50 random samples taken showed an average of 3.20 ppm PCBs, with
0,23 scattering ppm (squared).
Calculate:
A: are the results of the analysis is conclusive proof that it is necessary to stop production
B: is based on the analysis necessary to reduce the concentration of PCBs in the effluent
C: if you were the head of the factory, what would be your action on the basis of the analysis carried out

2. Jul 6, 2010

### Tedjn

Re: Statistics

Please show us what work you have done on this problem, so that we can better help you. In particular, what do you think would constitute as conclusive proof?

3. Jul 6, 2010

### jingjang

Re: Statistics

n=50
x=3ppm
xi=3.2ppm
s2=0.23ppm2
s=0.48ppm
λ=(3.2ppm-3ppm)/0.48ppm=0.42

hmmm...

4. Jul 6, 2010

### jingjang

Re: Statistics

or is it like this
t=(3.2ppm-3ppm)/0.48ppm * √n =2.97
H(S=95%,n-1) x=μ--> t=2.0092
2.97<2.0092 (not true)
H(S=99%, n-1) x≠μ t=2.6802
2.97>2.6802 (true)