Statistical Analysis Practice Problems

[RedX]

I couldn't figure out the standard deviation of the problem and I got confused on how to get the percentage. I also need these problems before 7:00 a.m. because I have to leave for school. I'm three tests tomorrow also. Please Help! Here are the problems:

#2. In this experiment, the student measured the percentage of chlorine (Cl) in an experiment for a total of five times. The student wants to find out the standard deviation for the data set, with particular interest in the range of values from one sigma below the mean to one sigma above the mean.

Trial 1 2 3 4 5
% of Cl 19.82 19.57 19.68 19.71 19.75


#3 A student analyzing a sample for bromine (br) make four trials with the following results:

Trial 1 2 3 4
% of Br 36.0 36.3 35.8 36.3

[dr_bilge]

I don't think it would help you if someone simply gave you the answer, but perhaps an easy way to remember how to calculate the standard deviation would help:

The "variance" is "mean of the squares (of each value) minus the square of the mean". The standard deviation is the square root of the variance.

If you want to have a go and replying with what you now think the answer is, I'm willing to check back and see if you're right