Question

.In a study of 225 adults, the mean heart rate was 72 beats per minute. Assume the population of heart rates is known to be approximately normal with a standard deviation of 10 beats per minute. What is the 90% confidence interval for the mean beats per minute?

70.7 – 73.3

70.9 – 73.1

70.7 – 73.1

70.9 – 73.3

Answer 1

@UnkleRhaukus

Answer 2

@Compassionate

Answer 3

@midhun.madhu1987

Answer 4

I am not good at this.. :(

Answer 5

The confidence interval for the mean is:
\[\large (\bar {x}-z\frac{\sigma}{\sqrt{n}}, \bar{x}+z\frac{\sigma}{\sqrt{n}})\]
where z is 1.645 to find a 90% confidence interval.
Plugging in the given values we get:
\[\large CI=([72-1.645\frac{10}{\sqrt{225}}],\ [72+1.645\frac{10}{\sqrt{225}}])\]
which simplifies to:
\[\large CI=([72-1.1], [72+1.1])\]
You can do the final arithmetic.