een asked by Forest Hill Elementary School to evaluate the school's drinking water. The lab tested 24 water specimens and found that the averaged lead concentration level was 8.43 pp (parts per billion) with a standard deviation 1.12 bbp. Give a 99% confidence interval for the true average lead level of Forest Hill Elementary School's dr
The deeply laboratory has been asked by Forest Hill Elementary School to evaluate the school's drinking water. The lab tested 24 water specimens and found that the averaged lead concentration level was 8.43 pp (parts per billion) with a standard deviation 1.12 bbp. Give a 99% confidence interval for the true average lead level of Forest Hill Elementary School's drinking water.
We have,
NOTE: As the population standard deviation is not given to us, we will use t confidence interval because the t-test/confidence interval approach is used when the population standard deviation is unknown.
The degree of freedom is calculated as:
df=n-1=24-1=23
We need to first obtain the critical value. Observe \alpha=0.01 and df=23 in the t-statistical table to obtain the critical value.
The answer is 2.807.
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