This is my sample: 29,083 ; 25,314, 31,920 ; 30,750 ; 32,302

Question

I need to find the mean and standard deviation of this sample?!

How can i assure the life spans are normally distributed?

Answer 1

for the mean, add them up and divide by 5

for the sd:
take the difference between each of the data values and the mean and square that result
repeat for all 5 of them
add them up, divide by either 5 or 4 depending on the definition of sd you are using, take the square root.

http://www.wolframalpha.com/input/?i=mean+29083%2C+25314%2C+31920%2C+30750%2C+32302

http://www.wolframalpha.com/input/?i=standard+deviation+29083%2C+25314%2C+31920%2C+30750%2C+32302

Answer 2

thank you but how can I assume that the life spans are normally distributed?