evaluating 16 natural logarithm 15-16 logic xv-xvi lower bounds, of rounded numbers 281-2 mathematical use z test cos pop std dev. given, but why I test use of and not o? Mixed Practice n 373 6 The blood oxygen levels (measured in percent) of an individual are known to be normally distributed with a standard deviation of 3%. Based upon six readings, Niamh finds that her blood oxygen levels are on average 88.2%. Find a 95% confidence interval for Niamh's true blood oxygen level. wod 7 The masses of chickens from two different farms are known to follow normal distributions, both with variance 0.36kg2. A sample of 12 chickens from the first farm had a mean mass of 2.4kg and the sample of 15 chickens from the second farm had a mean mass of 2.1 kg. A vet wants to test whether the mean fchick