The half-life of carbon-14 is 5,730 years. Suppose a fossil is found with 10 percent as much of its carbon-14 as compared to a living sample. How old is the fossil? 1904 years
38077 years
19039 years
3808 years

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.