Researchers measured the heart rates of several randomly selected astronauts exercising on stationary bicycles during long-term space missions. The researchers found the mean heart rate of the astronauts was 155 beats per minute with a margin of error of 12 beats per minute at a 90 percent confidence level. Which of the following is the most plausible value for the mean heart rate of all astronauts exercising on stationary bicycles during long-term space missions ?

1) 130 beats per minute

2) 140 beats per minute

3) 160 beats per minute

4) 175 beats per minute

Solution:

Choice C is correct.

Since, the mean heart rate of the astronauts was 155 beats per minute with a margin error of 12 beats per minute with a 90% confidence level.

Therefore, the true mean will be within the margin of error around the mean in thisparticular study.

Therefore true mean will be between (155 – 12) and (155 + 12) i.e. 143 and 167 only.

Only one of the given options fall within this range.

Therefore, the most plausible value for the mean heart rate for all astronauts would be 160 beats per minute.