Standard Deviation Calculation

Did you weight the values according to their probabilities?

but that way, we get expected values right? Do we also have to weigh the values according to their probabilities to calculate standard deviation? I calculated, mean, variance and square root of variance to calculate variance. How do use values for probability?

Regs

One way is to assume 5 entries each of 100,000 and 40,000; 10 each of 90,000 and 50,000; 20 each of 80,000 and 60,000, and 30 of 70,000; for a total N of 100.

Alternatively....

1 entry each of 100,000 and 40,000; 2 each of 90,000 and 50,000; 4 each of 80,000 and 60,000, and 6 of 70,000; for a total N of 20.

ie 100,90,90,80,80,80,80,70,70,70,70,70,70,60,60,60,60,50,50,40 _{(less typing and counting...)}

Stick that lot in a calculator and you do get 14.491 _{(you can do the x10³ in your head)}

Who cares about a poster who cannot go to the trouble of coming up with a nickname? A "nick" is just as anonymous, but it allows us to search your history, and frame an answer based on "getting to know you". Please consider it.

I'm not going to do your homework for you but I'd be curious to know how you calculated your answer. Your data set is chunky and evenly divided, given the way the normal curve calculations are performed it would be unusual indeed to arrive at a round number answer for such a data set. My brain tells me it should be around 14,140. What did you do, a 2 sigma calculation by ignoring the outliers and dividing the 40,000 spread by two?