Question

A drug company is testing a new drag which is supported to reduce blood pressure. From the nine people who are used as subjects, it is found that the average drop in blood pressure is 2.28 points, with a standard deviation of 0.82 points. What is the 95% confidence interval for the mean change in pressure?

Answer 1

Answer:

The 95% confidence interval for the mean change in blood pressure, $\bar{x}$, is 1.744 < $\bar{x}$ < 2.816

Step-by-step explanation:

The parameters given are;

The number of people in the sample, n = 9

The average drop in blood pressure, $\bar{x}$ = 2.28 points

The standard deviation, σ = 0.82

The confidence level = 95%

The formula for confidence interval with a known mean is given as follows;

$CI=\bar{x}\pm z_{\alpha/2} \dfrac{\sigma}{\sqrt{n}}$

Where:

$z_{\alpha/2}$ = z - score at 95% confidence level = 1.96

We therefore have;

$CI=2.28 \pm 1.96 \times \dfrac{0.82}{\sqrt{9}}$

Which gives the 95% confidence interval for the mean change in pressure, $\bar{x}$, is given as follows;

1.744 < $\bar{x}$ < 2.816