Question

Is wanted to dermine the avarage concentration of the lead in the water of a river. Is used a preliminar sample to estimate de variability.The preliminar sample indicates a standard deviation of $0.04\mu g$

A)To estimate the lead first we need to obtain the size of the sample to assure the experiment will be succesfull. Determine the size required to obtain an error in the estimation of the avarage of $0.05\mu g$ with the 90% of trust.

B)Obtain the interval of trust for the standar deviation(with a 99% of trust). Supose the standard deviation of a size 21 sample is of $0.37\mu g$ and the standard deviation of the poblation is $0.43\mu g$

C)Supose the standar deviation of a sample of size 21 is of $0.37\mu g$ and the standar deviation of the poblation is of $0.43\mu g$ . Calculate the probability that the stancard deviation of the sample will be less than $0.37\mu g$ .

0.37ug 0.43μg 0.37ug 0.37ug

Answer 1

Solution:

Bu tthe at a Ven 2一 ZSd 2 73-1856 o) 37 mula -시 2

Hence 97% confidence intewd apStandaVol Cle victton 2. - 0.27 0