The length of these bars should look like the 'typical' distance from the mean for these two samples. Another example of estimating mean and standard deviation is shown below. Your estimates should agree fairly well with the values you calculate by hand or using your computer. If they don't, then you have done the calculation wrong. These were estimated by eye.
Standard deviation is a measure of 'typical' distance from the mean.
When considering averages, we saw that the accuracy of estimates of population mean depend on sample size but that small samples, though unreliable, are unbiased. This is illustrated in the stem and leaf plot below showing the means of 40 samples drawn from a population with a mean of 100. However, the standard deviation of small samples tends systematically to be less than the standard deviation of the population from which they were drawn. This is illustrated in the table below. I then took 40 samples of 5 and 20 and calculated their standard deviation.