Question

In a study of 250 adults, the mean heart rate was 70 beats per minute. Assume the population of heart rates is known to be approximately normal with a standard deviation of 12 beats per minute. What is the 99% confidence interval for the mean beats per minute?

68.9 – 76.3

70 – 72

61.2 – 72.8

68 – 72

Answer 1

I got it.

Answer 2

For a 99% C.I., for have \(\alpha=0.01\).
\[ \left[\bar{x}-Z_{\alpha/2}\frac{s}{\sqrt{n}}, \,\,\bar{x}+Z_{\alpha/2}\frac{s}{\sqrt{n}} \right]\]
You can verify on a table that the corresponding z-value should be 2.575
\[ \left[70-2.575\cdot\frac{12}{\sqrt{250}}, \,\,70+2.575\frac{12}{\sqrt{250}} \right]\]

Answer 3

@brooklynransome found the answer?