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 315 police officers from the same city. (the lower the measure of hrv, the more susceptible the officer is to cardiovascular disease.) for the 68 officers diagnosed with hypertension, a 90% confidence interval for the mean hrv was (9.5,122.4). for the 247 officers that are not hypertensive, a 90% confidence interval for the mean hrv was (144.7,185.9). a. what confidence coefficient was used to generate the confidence intervals?