Help with some simple mean, averages, ect

use this guy: https://www.easycalculation.com/statistics/standard-deviation.php (it shows all the info you want if you type in those 4 numbers)

92.75
13.1751
for the third one, create a z variable with this formula https://www0.gsb.columbia.edu/premba/analytical/images/s6/5836240103.gif and then use this page to learn about finding the probability https://www0.gsb.columbia.edu/premba/analytical/s6/s6_4.cfm (if you know this stuff just skip to a table of Z values and you're done!)

 

This. While often the Z table isn't applicable to sample means and standard deviations it's likely assumed in this case it does.

 

I looked at the site, i did 90(because its a chance of 90g) - the mean over the standard deviation, but the answer I got was wrong. Can anyone else help?

 

A) 92.75 as stated above
B) N/A
C) I got 0.53 but I might be wrong :x

 

Z = (90 - 92.75)/13.1751 = -0.2087
then use a z stat table like this one http://www.stat.ufl.edu/~athienit/Tables/Ztable.pdf
go over from -0.2 to the 0.09 column (since -0.2087 rounds to -0.209), and you get 0.3859. also this makes sense logically. if the mean is a bit more than the number you're concerned with, it would make sense that the probability is a bit less than half

 

Actually I think the probability is closer to .417, as the columns represent the hundredths digits (i.e. -0.20 to -0.29), so we would look at the -0.2 row and the .01 column which gives .4168, but we would expect it to be a little higher than that because we rounded up. Wolframalpha gives a similar result: http://www.wolframalpha.com/input/?i=probability+that+z<=-.2087