Question 1181115: A sample of 16 Ten-Years old girls had a mean weight of 71.54 pounds and a standard deviation of 12 pounds.
(a) What assumption is necessary for the validity of the confidence interval constructed?
(b) What is the estimated standard error?
(c) Construct a 95% confidence interval for the population mean.
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! Assumptions are the the population is 10 year-olds girls, that the sample selected is random, the distribution is normal, and that the sd of the sample may be used in place of the unknown sd of the population.
the SE is s/sqrt(16)=12/4=3 pounds
the 95% CI half-interval is t(0.975, df=15)*SE=2.131*3=6.39 pounds
the interval is ((65,15, 77.93) units pounds
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