The following data set lists ages of deceased US Presidents at their death 67 73 68 74 66 57 60 60 78 93 90 80 71 64 63 71 72 90 46 93 83 78 53 77 70...

The following data set lists ages of deceased US Presidents at their death

67 73 68 74 66 57 60 60 78 93 90 80 71 64 63 71 72 90 46 93 83 78 53 77 70 67 67 63 84 85 79 65 56 49 58 57 88 81

1)Manually estimate the mean, variance, and standard deviation of the ages of the Presidents at their death using the frequency distribution

2) Manually calculate the actual mean, variance and standard deviation of ages of PResident.  Is this data a sample or a population?

3) Does calculator give you the mean and standard deviation you found in #1 and #2? Why?

I'm not sure what is the difference between estimate and then calculated

 in question 2.  Can someone explain this in detail since I have several to do like this.