Standard deviation- geographical skills

What is standard deviation?

• is a statistic that tells you how tightly data is clustered around the mean

• A low or small standard deviation indicates data is clustered tightly around the mean

• A high or large deviation indicates data is more spread out

• A standard deviation close to 0 indicates that the data points tend to be close to the mean

What are the limitations of standard deviation ?

• If data isn’t distributed properly it is not appropriate to use sd

• The calculation can be time consuming

• The deviation can only be compared between samples of comparable populations e.g. you can’t compare an SD for a litter layer depth with a SD for soil Ph

Why is standard deviation useful?

• smaller standard deviations reflect more clustered data

• More clustered data means less extreme values

• A data set with less extreme values has a more reliable mean

• The standard deviation is a good measure of the reliability of the mean value

What is central tendancy?

Describes a set of data by identifying the central position in the data set as a single value- 3 most common mean, mode, median