A marine biologist would like to estimate the mean lifespan of all Florida manatees. The mean lifespan of a random sample of 43 Florida manatees was found to be 55.5 years. The standard deviation of the lifespans of all Florida Manatees is known to be 8.5 years. Using a 90% confidence level, determine a confidence interval for the mean lifespan of all Florida Manatees. Report the confidence interval using interval notation. Round solutions to two decimal places, if necessary. A 90% confidence interval is given by . Suppose the population standard deviation was unknown, but the marine biologist found the standard deviation of the lifespan of the sample of 43 Florida manatees was 9.8 years (along with the sample mean of 55.5 years). Determine a 90% confidence interval for the mean lifespan of all Florida manatees using this new information A 90% confidence interval is given by