The range of a sample is the difference between the minimum (lowest number) and the maximum (highest number).
In the sample given, the lowest number is 6.4 and the highest number is 38, so the range is 38-6.4=31.6.
The variation is a bit trickier, but easily done once you know how. It is the sum of the squared differences between each number and the mean of all the numbers, all divided by the number of numbers.
Σ(xi-mean(x))2/n
In the sample given the mean is 19.73. This is found by adding all the numbers and dividing by how many there are: (38+36+35+27+17+13+11+7+6.9+6.4)/10
Using that, we can find the variance:
[(38-19.73)2+(36-19.73)2+(35-19.73)2+(27-19.73)2+(17-19.73)2+(13-19.73)2+(11-19.73)2+(7-19.73)2+(6.9-19.73)2+(6.4-19.73)2]/10=151.7841
The standard deviation is just the square root of the variance:
st.dev=√(var)
In the sample given, the standard deviation is the square root of 151.7841, which equals 12.32.
