private static void InsertStandardDeviationFormula(XWPFParagraph p)
{
var math = p.CreateOMath();
math.CreateRun().SetText("\u03c3=");
var rad = math.CreateRad();
rad.Degree.CreateRun().SetText("2");
var f = rad.Element.CreateF();
f.FractionType = ST_FType.bar;
f.Denominator.CreateRun().SetText("n-1");
var nary = f.Numerator.CreateNary().SetSumm();
nary.Superscript.CreateRun().SetText("n");
nary.Subscript.CreateRun().SetText("i=1");
var ssup = nary.Element.CreateSSup();
ssup.Element.CreateRun().SetText("(");
var ssub = ssup.Element.CreateSSub();
ssub.Element.CreateRun().SetText("X");
ssub.Subscript.CreateRun().SetText("i");
ssup.Element.CreateRun().SetText("-");
var acc = ssup.Element.CreateAcc();
acc.AccPr = "¯";
acc.Element.CreateRun().SetText("X");
ssup.Element.CreateRun().SetText(")");
ssup.Superscript.CreateRun().SetText("2");
}