public static Nullable<double> StandardDeviationSample<TSource>(
	this IEnumerable<TSource> source,
	Func<TSource, Nullable<int>> selector
)

<ExtensionAttribute>
Public Shared Function StandardDeviationSample(Of TSource) ( 
	source As IEnumerable(Of TSource),
	selector As Func(Of TSource, Nullable(Of Integer))
) As Nullable(Of Double)

[<ExtensionAttribute>]
static member StandardDeviationSample : 
        source : IEnumerable<'TSource> * 
        selector : Func<'TSource, Nullable<int>> -> Nullable<float>