How do you find average and standard deviation on a histogram?

Question

I have an assignment for school where I need to read a histogram, but the class did not go over how to read a histogram or how to calculate average or standard deviation.

Here's a picture of the histogram (follow this link): http://www.catanzareti.com/images/Kevin/histogram.jpg

The first question is: Estimate the average metallicity for stars with planets and for field stars.

The second question is: estimate the standard deviation of the field stars.

I don't know how to calculate these figures. Could someone help and explain how I'd find these?

THANKS!

Answer 1

First off you need to know how to read the histogram Here's some links that will help
http://mathworld.wolfram.com/Histogram.html
http://www.sparknotes.com/math/algebra1/graphingdata/summary.html
or if you want something written on a nice basic level...
http://www.studyzone.org/mtestprep/math8/f/histograml.cfm
Next you need to know how to find the mean and standard deviation for the information yo'uve read from the histogram.
How to find a mean and standard deviation for grouped data:
http://mathforum.org/library/drmath/view/52199.html
http://www.bjmath.com/bjmath/Stats/sd.htm

Answer 2

Did you really think the person didn't know that? What a maroon.