In a survey, 31 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $49 and standard deviation of $8. Find the margin of error at a 80% confidence level. Give your answer to two decimal places.

Compare the subtraction problems 6/8 - 5/8 = 1/8 and 6/9 - 7/9 = 1/9 why is the answer to the first problem positive and the answer to the second problem negative

Explain why the factor 1.5 is broke. into two numbers in the model.

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.