What is standard error bar in graphs?

Answer 1

This question requires care to prevent confusion, and a basic knowledge of statistics. I've seen three types of descriptive statistical error bar used: standard deviation, standard error, or confidence interval. The use of any of these indicates that each point in the graph around which error bars are placed is the mean of a set of values. The error bars then give an indication of this set of data: * Standard deviation gives an indication of the variability of the underlying set of values. * Standard error gives an indication of how close the calculated mean of the set of values is to the mean of the entire population of these values (this is dependant on the number of these values the mean is found from - the greater the number of values used, the smaller the standard error). * The condfidence interval is the range which is likely to contain the true population mean (and is thus related to the standard error). Each of these may be used depending on the data used. However, you have to be careful since the first two of these are often confused - and the type of error bar used is often not labelled at all. Hope that helped :-)