RandomNormal[μ_,σ_]:=Random[NormalDistribution[μ,σ]]

Prepare some random numbers following the normal distribution

data=Table[RandomNormal[5,1],{100}];

<<"StatisticalPlots`"

Mean[data]

StandardDeviation[data]

The mean is not very sensitive to outliers

dataplus=Join[data,{0.3,8.1,9.9}];

Mean[dataplus]

TrimmedMean[dataplus,{1/100,1/100}]

TrimmedMean[dataplus,{2/100,2/100}]

The standard deviation is more sensitive to outliers

StandardDeviation[dataplus]

Definition of Box, Near and Far Outliers :
The default box spans from the 0.25 quantile to the 0.75 quantile.
Near outliers are defined as points beyond (3/2) times the interquantile range from the edge of the box. Far outliers are defined as points beyond three times that range.

BoxWhiskerPlot[data,dataplus]

BoxWhiskerPlot[dataplus,BoxOutliers->All,BoxOutlierMarkers->{,}]

Build a histogram of data:

Histogram[data]

Histogram[dataplus,{0,10, .5}]