Question

type the answers please. Thanks :)

1) When people smoke, the nicotine they absorb is converted to cotinine, which can be measured. A random sample of 40 smokers has a mean cotinine level of 172.5. Assuming that is known to be 119.5, find a 94% confidence interval estimate of the mean cotinine level of all smokers. Write a sentence that interprets this interval. 2) You want to estimate the mean weight loss of people one year after following the Atkins diet. How many dieters must be surveyed if we want to be 95% confident that the sample mean weight loss is within 0.25 pound of the true population mean? Assume that the population standard deviation is known to be 10.6 lb.

Answer 1

1)

sample mean sample size population std deviation X= 172.5000 40.00 n= 119.500 standard errror of mean ao/Vn 18.8946 for 94 % Cl value of z 1.88 margin of error E-z"std error 35.54 lower confidence bound-sample mean-margin of error= Upper confidence bound-sample mean +margin of error= 136.96 208.04

from above 94% confidence interval =136.94 , 208.04

above interval gives 94% confidence to contain true population mean of cotinine

2)

	for95% CI crtiical Z          =	1.96
	standard deviation σ=	10.6
	margin of error E =	0.25
required sample size n=(zσ/E)2                  =		6907