It is well-established that systolic blood pressure for the US population is a normally-distributed variable centered around a mean of 120 mmHg with a standard deviation of 12 mmHg. A researcher studying inhabitants of a small town in rural North Carolina suspects the town's residents have a significantly lower systolic blood pressure than the US population. Data collected from a random sample of 9 residents from the rural town demonstrates a mean systolic blood pressure of 111 mmHg. Based on this data, can it be stated that the residents of the rural town have a mean systolic blood pressure significantly lower than the US population at the (a) 95% confidence level? (b) 99% confidence level?
Added by Gregory L.
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We are given the population mean ($\mu$) and population standard deviation ($\sigma$) for systolic blood pressure in the US: $\mu = 120$ mmHg and $\sigma = 12$ mmHg. Show more…
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