(Ignore this answer; Vince has a much better approach.)
 
A variation on Vince's answer, if you want per-file statistics.  I also imagine the columns are consistent...
 
path = "$desktop/csvFiles/";
files = Files In Directory( path );
answers = New Table( "Summary",
	New Column( "N Rows", Numeric, "Continuous", Format( "Fixed Dec", 12, 0 ), Set Values( [] ) ),
	New Column( "Mean(x)", Numeric, "Continuous", Format( "Best", 12 ), Set Values( [] ) ),
	New Column( "Mean(y)", Numeric, "Continuous", Format( "Best", 12 ), Set Values( [] ) ),
	New Column( "Mean(z)", Numeric, "Continuous", Format( "Best", 12 ), Set Values( [] ) ),
	New Column( "sourceFile", character )
);
For( iFile = 1, iFile <= N Items( files ), iFile += 1,
	file = path || files[iFile];
	dt = Open( file, "text" );
	dt2 = dt << Summary( Mean( :x ), Mean( :y ), Mean( :z ), Freq( "None" ), Weight( "None" ) );
	answers << addrows( 1 );
	answers:sourceFile = file || " " || Format( Creation Date( file ), "m/d/y h:m:s" );
	answers:N Rows = dt2:N Rows[1];
	answers:name( "Mean(x)" ) = dt2:name( "Mean(x)" )[1];
	answers:name( "Mean(y)" ) = dt2:name( "Mean(y)" )[1];
	answers:name( "Mean(z)" ) = dt2:name( "Mean(z)" )[1];
	Close( dt, nosave ); // linked table closes too
);
my files looked like this
x,y,z
1,2,3
4,5,6
 
I used the table script from a file I made by hand to get the Summary script.  There might be a better way to copy the variables; in JMP 13 you could use the ideas here to assign a whole row in one statement.
 
					
				
			
			
				
	Craige