Sull'asse verticale è rappresentata la frequenza percentuale unitaria (o densità)
On the y axis, the unitary percentage frequency (or density) is represented
(that is the percentage frequencies divided by the amplitude of each interval).
You can round mean and sigma (taking into account the width of the intervals).

Puoi aprire il codice e modificare la funzione: vedi l'Help
You can open the Code and modify the function: see the Help
HELP

// I: estremi degli intervalli, P: frequenze
I=[53.5, 60.5, 67.5, 74.5, 81.5, 88.5, 95.5, 102.5, 109.5, 116.5, 123.5, 130.5 ]
P=[    4,   39,  122,  197,   192,  126,   93,    33,    16,     2,     1]; NP=P.length

Tot=0; for(i=0;i<NP;i=i+1) {Tot=Tot+P[i]}; for(i=0;i<NP;i=i+1) {P[i]=P[i]/Tot/(I[i+1]-I[i])}
LLx=[]; j=0; for(i=1;i<=NP;i=i+1) { LLx[j]=I[i-1]; LLx[j+1]=I[i-1]; LLx[j+2]=I[i]; LLx[j+3]=I[i]; j=j+4 }
LLy=[]; j=0; for(i=1;i<=NP;i=i+1) { LLy[j]=0; LLy[j+1]=P[i-1]; LLy[j+2]=P[i-1]; LLy[j+3]=0; j=j+4 }

aX = 50; bX = 135; aY = 0; bY = 0.04
Dx = 5; Dy = 0.005
XX=[100]; YY=[0.01,0.02,0.03]

mean=84.2957; sigma=11.5
function f(x) { y = Math.exp( -Math.pow((x-mean)/sigma,2)/2) / Math.sqrt(2*Math.PI)/sigma; return y }
...
yy=YY; xx=XX
Q1x=[mean]; Q1y=[0]
C1="black"
L1x=LLx; L1y=LLy
...
AX=BX=AY=BY=""
BY = "Tot="+Tot;  AY = "mean="+mean
AAX=aX; BBX=bX; AAY=aY; BBY=bY