# How to find confidence interval and perfrom one tailed t tes

Let x be a random variable representing percetage of carboxyhemoglobin in the blood. For a person who is a regular heavy smoker, x has a distribution that is approximately normal. A random sample of n= 12 blood test given to a heavy smoker gave the following results:

9.1 9.5 10.2 9.8 11.3 12.2

11.6 10.3 8.9 9.7 13.4 9.9

a) Use a calculator to verify that x?10.49 and s?1.36

b) A long term population mean ? = 10% is considered a health risk. However, a long-term population mean above 10% is considered a clinical alert that the person may be asymptomatic. Do the data indicate that the population mean percentage is higher than 10% for this patient? Use ? = 0.05

c) Use the given data to find a 99% confidence interval for ? for this patient.

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#### Solution Preview

a) I verified the mean and standard deviation with the calculator.

b) Null hypothesis: the population mean percentage is smaller or equal to 10%.

Alternative hypothesis: the population mean ...

#### Solution Summary

The solution provides detailed explanation how to find confidence interval and perform one tailed t test.