are these answers correct?

(12.5 pts) A sample of 25 healthy adults who work in the same office had a mean hemoglobin reading of 16 g/100 ml. In the general population, it is known that hemoglobin is normally distributed and has a variance of 4 g/100 ml. What is the 95% confidence interval for the population mean? (0.3168, 0.0032) . (12.5 pts) It was found that a sample of 30 students have a mean serum cholesterol level of 217 with a standard deviation of 39. Construct a 90% confidence interval for the population mean. (204.90, 229.10) . (12.5 pts) A random sample of 81 males had a mean weight of 177 lbs. The mean weight of all males in the US is 170 lbs with a variance of 225. What is the 99% confidence interval for the population mean? (172.707, 181.293) . (12.5 pts) A sample of 17 nursing students were found to get an average of 300 minutes of sleep each night with a variance of 144. Construct a 95% confidence interval for the population mean. (294.295, 305.705)