Here's the problem Jack and Jill are trying to solve: -19 = ? Jack thinks the answer is -9, because the negative is outside the absolute
value signs.
Jill thinks the answer is 9, because the teacher said absolute value is
always positive.
Who is right and why? Explain your steps using sentences.

Afactory makes propeller drive shafts for ships. a quality assurance engineer at the factory needs to estimate the true mean length of the shafts. she randomly selects four drive shafts made at the factory, measures their lengths, and finds their sample mean to be 1000 mm. the lengths are known to follow a normal distribution whose standard deviation is 2 mm. calculate a 95% confidence interval for the true mean length of the shafts. input your answers for the margin of error, lower bound, and upper bound.