Ferric chloride is used as a flux in some types of extraction metallurgy processes. this material is shipped in containers, and the container weight varies. it is important to obtain an accurate estimate of mean container weight. suppose that from long experience a reliable value for the standard deviation of flux container weight is determined to be 4 lb. how large a sample would be required to construct a 95% two-sided confidence interval on the mean that has a total width of 1 lb?

222

Step-by-step explanation:

As considering the given description, we have

Population standard deviation:

Margin of error : E = half of width of confidece interval

=

Critical value for 95% confidence interval :

Formula to find the sample size :

i.e.

Hence, the required minimum sample size = 222

the answer   is 200

step-by-step explanation:

this is a problem about poisson probabilities.   i don't know if you've

already studied poisson distributions, or if you have a place to look

to read more about the subject.  

here's how you can see a poisson distribution coming.   when there are

a lot of events that may happen at any time (or any place), and when

you're counting how many of them happen at a particular time (or a

particular place), and each event is independent of the others, then

the result is a poisson distribution.   this is roughly true for the

chocolate chips; one chip being in a cookie has only a small effect on

the probability that another chip will be in the cookie.

once you know you have a poisson distribution, you know a lot.   there

is only one parameter to a poisson distribution, so if you know the

mean, you know everything.   the form of the distribution is

  probability of n chips = {[e^(-x)]*(x^n)} / (n! )