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 368 police officers from the same city.​ (The lower the measure of​ HRV, the more susceptible the officer is to cardiovascular​ disease.) For the 76 officers diagnosed with​ hypertension, a 90​% confidence interval for the mean HRV was ​(454.5​,129.6​). For the 292 officers that are not​ hypertensive, a 90​% confidence interval for the mean HRV was ​(153.9,195.5​). Use this information to complete below parts.
a. What confidence coefficient was used to generate the confidence intervals?
b. Give a practical interpretation of both of the 99% confidence intervals. Use the phrase "99% confident" in your answer.