Martha is planning to survey people at a water park to determine the most popular water slide at the park. which would be the best sample for her survey to draw a valid inference? a. children at the park between the ages of 3 and 5 b. children at the park between the ages of 6 and 10 c. adults at the park between the ages of 20 and 30 d. adults and children of all ages at the park

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.