The heart rate variability​ (HRV) of police officers was the subject of research published in a biology journal. HRV is defined as the variation in the time intervals between heartbeats. A measure of HRV was obtained for each in a sample of 308police officers from the same city.​ (The lower the measure of​ HRV, the more susceptible the officer is to cardiovascular​ disease.) For the 79 officers diagnosed with​ hypertension, a 95% confidence interval for the mean HRV was ​(9.4​,129.1​).

For the 229 officers that are not​ hypertensive, a 95​% confidence interval for the mean HRV was (145.7​,188.6​).

Use this information to complete parts a through d below.

a. What confidence coefficient was used to generate the confidence​ intervals?

b. Give a practical interpretation of both of the 95​% confidence intervals. Use the phrase "95​% confident" in your answer.

The researchers can be 95​% confident that the true mean HRV for all hypertensive police officers in the city is between __ and __. A similar statement can be made about the police officers without hypertension.​(Type integers or decimals. Do not​ round.)