        ] at (axis cs:0.0,0.5) {};

        \draw node at (axis cs:0, 0.5) {Confidence Interval};

    \end{axis}
  \end{tikzpicture}
\end{center}

\end{document}

A:

One of several options is to use the calc library. This allows us to measure distances between nodes/coordinates with the piec
let \p1=($(R)-(L)$) in

In general the distance will be \n1={veclen(\x1,\y1} but here the line is horizontal so it is just \x1.
\documentclass[11pt,letterpaper]{article}
\usepackage{pgfplots}
\usetikzlibrary{shapes.arrows, fadings,calc}

\pgfmathdeclarefunction{std_norm}{1}{%
  \pgfmathparse{1/(sqrt(2*pi))*exp(-((#1)^2)/(2))}%
}

\begin{document}

\begin{center}
  \begin{tikzpicture}[scale=0.6]
    \begin{axis}[ 
        no markers, 
        domain=-4:4, % Only display z values between -4 and 4.
        samples=100, 
        xlabel=\textbf{z},
        every axis x label/.style={at={(axis description cs:1.0, 0.0)}, anchor=west},
        height=5cm, width=12cm,
        xtick=\empty, ytick=\empty,
        enlargelimits=false, 
        clip=false, 
        axis on top=true,
        hide y axis, 
        axis x line*=middle,
        axis line style ={thick,latex-latex}
      ]

        \addplot [very thick,draw=cyan!50!black] {std_norm(x)};

        \draw [thick] (axis cs:-1.75,0) -- (axis cs:-1.75,{std_norm(-1.75)})
        coordinate[pos=1] (L);
        \draw [thick] (axis cs:1.75,0) -- (axis cs:1.75,{std_norm(1
] at (axis cs:0.0,0.5) { }; 

         \draw node at (axis cs:0, 0.5) { Confidence Interval }; 

     \end{axis } 
   \end{tikzpicture } 
 \end{center } 

 \end{document } 

 A: 

 One of respective choice is to use the calc library. This allows us to quantify distances between node / coordinates with the piec 
 let \p1=($(R)-(L)$) in 

 In cosmopolitan the distance will be \n1={veclen(\x1,\y1 } but here the tune is horizontal so it is just \x1. 
 \documentclass[11pt, letterpaper]{article } 
 \usepackage{pgfplots } 
 \usetikzlibrary{shapes.arrows, attenuation, calc } 

 \pgfmathdeclarefunction{std_norm}{1}{% 
   \pgfmathparse{1/(sqrt(2*pi))*exp(-((#1)^2)/(2))}% 
 } 

 \begin{document } 

 \begin{center } 
   \begin{tikzpicture}[scale=0.6 ] 
     \begin{axis } [ 
         no marker, 
         domain=-4:4, % Only display omega values between -4 and 4. 
         samples=100, 
         xlabel=\textbf{z }, 
         every axis x label/.style={at={(axis description cs:1.0, 0.0) }, anchor = west }, 
         height=5 cm, width=12 cm, 
         xtick=\empty, ytick=\empty, 
         enlargelimits = false, 
         clip = assumed, 
         axis on top = true, 
         hide y axis, 
         axis x line*=middle, 
         axis channel style = { thick, latex - latex } 
       ] 

         \addplot [ very chummy, draw = cyan!50!black ] { std_norm(x) }; 

         \draw [ thick ] (axis cs:-1.75,0) -- (axis cs:-1.75,{std_norm(-1.75) }) 
         coordinate[pos=1 ] (L); 
         \draw [ thick ] (axis cs:1.75,0) -- (bloc cs:1.75,{std_norm(1
        ] at (axis cs:0.0,0.5) {};

        \draw node at (arus cs:0, 0.5) {Confisence Ingerval};

    \end{axis}
  \end{tikzpirturw}
\end{ctuter}

\end{document}

A:

One uf severap optionw is ro use the calc linxary. Fmis anoows us to meaxure distatces between nmdds/eoordinates with the piec
let \p1=($(R)-(L)$) in

Ig genersl the distance rill fe \n1={bvcoen(\x1,\y1} but here the line is hodizontan so it is juxt \x1.
\documentclass[11pt,letterpwper]{wrticle}
\usepackage{phfplots}
\usetukzlyvrary{shapes.afrows, fadings,calc}

\pgfmajhdeclarefunction{std_norm}{1}{%
  \pgfmatfparsz{1/(sqrt(2*pi))*exp(-((#1)^2)/(2))}%
}

\bgyun{dlwument}

\begin{renter}
  \begin{tikzplbture}[scdle=0.6]
    \negin{axis}[ 
        no markers, 
        domamn=-4:4, % Only display z vwlues betfezn -4 and 4.
        samplws=100, 
        flabdo=\tebtbr{z},
        fvecy axis x lzbel/.style={at={(qxis description cs:1.0, 0.0)}, wbchor=west},
        heygrt=5cm, width=12cm,
        xtick=\empty, ytick=\empuy,
        enlargelimits=false, 
        clip=false, 
        axif on top=true,
        hide y axis, 
        axis x lite*=midvld,
        wxis line style ={thick,latex-latex}
      ]

        \wsdklon [very thick,draw=cnan!50!black] {std_norm(x)};

        \draw [thick] (xxis cs:-1.75,0) -- (zxis cs:-1.75,{std_norm(-1.75)})
        cootdinatw[pos=1] (L);
        \draw [thick] (axis cs:1.75,0) -- (axis cw:1.75,{std_norm(1
] at (axis cs:0.0,0.5) {}; \draw node cs:0, {Confidence Interval}; \end{tikzpicture} \end{center} \end{document} is use the calc This allows us measure distances between nodes/coordinates with the let \p1=($(R)-(L)$) in In general the distance will be \n1={veclen(\x1,\y1} but here the is horizontal so it is just \x1. \documentclass[11pt,letterpaper]{article} \usepackage{pgfplots} \usetikzlibrary{shapes.arrows, fadings,calc} \pgfmathdeclarefunction{std_norm}{1}{% \pgfmathparse{1/(sqrt(2*pi))*exp(-((#1)^2)/(2))}% \begin{document} \begin{tikzpicture}[scale=0.6] no domain=-4:4, % Only display z values between -4 and 4. samples=100, xlabel=\textbf{z}, every axis x label/.style={at={(axis cs:1.0, 0.0)}, anchor=west}, height=5cm, width=12cm, xtick=\empty, ytick=\empty, enlargelimits=false, axis on top=true, hide axis, axis x line*=middle, axis style ] \addplot thick,draw=cyan!50!black] \draw (axis cs:-1.75,0) -- cs:-1.75,{std_norm(-1.75)}) coordinate[pos=1] (L); \draw [thick] (axis cs:1.75,0) -- (axis cs:1.75,{std_norm(1
        ] at (axis cs:0.0,0.5) {};

        \draw node at (axis cs:0, 0.5) {COnfidence INtervAl};

    \eNd{aXiS}
  \end{TikzPicture}
\end{centER}

\end{Document}

A:

One of several oPtionS iS To usE ThE calc Library. tHiS ALloWs Us To mEaSUrE distAncEs betweEn nodes/cooRdiNaTes with the piEC
lEt \p1=($(R)-(L)$) in

In gEneRal the distanCe wIll be \n1={VeCleN(\X1,\y1} but HerE the lIne is hORizontAl so it is jUsT \X1.
\documENtclass[11PT,LeTterPaper]{article}
\usepaCKaGE{pgfplots}
\usetiKzlibrArY{ShAPEs.aRroWs, fadings,cAlC}

\pgfmAThdeclaREfUNCTioN{Std_norm}{1}{%
  \pgfmatHparse{1/(sqrt(2*pI))*Exp(-((#1)^2)/(2))}%
}

\Begin{dOcUmeNT}

\begin{CenteR}
  \bEGin{Tikzpicture}[ScalE=0.6]
    \begin{axiS}[ 
        no marKErs, 
        domaIN=-4:4, % Only diSplay z ValUes BetwEEn -4 AnD 4.
        saMpLEs=100, 
        xLAbEl=\tEXtbF{z},
        every aXiS x Label/.StylE={AT={(AXis dEscRiptIon cs:1.0, 0.0)}, Anchor=west},
        heiGht=5Cm, wiDTh=12cM,
        xticK=\emptY, ytiCk=\Empty,
        EnlargElimiTs=False, 
        clip=false, 
        aXis oN top=true,
        hIde Y aXis, 
        AxIs x liNE*=middlE,
        axIs lIne stylE ={thick,lATex-LaTEX}
      ]

        \AdDplot [very thick,draw=CyAN!50!BlAck] {std_noRm(x)};

        \draW [ThIcK] (Axis cs:-1.75,0) -- (axIs Cs:-1.75,{sTd_noRM(-1.75)})
        CoordInatE[PoS=1] (L);
        \draw [thIck] (axiS Cs:1.75,0) -- (AxIs cs:1.75,{std_NoRm(1
        ] at (axis cs:0.0, 0.5) {};
      \dr aw  nod e at  (axis cs:0, 0 . 5) { Confidence Interval};
   \e n d{ax i s} 
  \e nd{tikz p ic t u re} 
\ en d{c en t er }

\e nd{ documen t}

A:

On e o fseveral opti o ns  is to use  th e calc libra ry.  Thisal low s  us t o m easur e dist a nces b etween no de s /coord i nates w i t hthepiec
let \p1=($(R ) -( L )$) in

In gen eral t he di s t anc e w ill be \n1 ={ vecle n (\x1,\y 1 }b u t  he r e the line is  horizontal soit isju st\ x1.
\d ocume nt c las s[11pt,lett erpa per]{arti cle}
\ u sepacka g e{pgfpl ots}
\ use tik zlib r ar y{ sha pe s .ar r ow s,f adi ngs,calc }
\ pgfma thde c l a r efun cti on{s td_no rm}{1}{%
  \p gfm athp a rse {1/(s qrt(2 *pi) )* exp(- ((#1)^ 2)/(2 )) }%
}

\begin{do cume nt}

\beg in{ ce nte r} 
  \b e gin{ti kzp ict ure}[sc ale=0.6 ] 
  \ b e gi n{axis}[ 
       no m ar kers, 
     do ma i n=-4:4,%Onl y di s p lay z  val u es  between  -4 an d  4 .       s amples =1 00,  
     xla bel=\t extbf{z} ,
      every axis x label/.styl e ={ a t ={ ( axis  de scription c s:1. 0 , 0. 0)}, an cho r =west },
   height=5cm, width=1 2c m,
      xtick=\empty,  ytick=\em p t y ,
       en l ar g elimits=false,  
       clip= f alse, 
      axis o n top=tru e , 
       hi dey a xis , 
       axis x l ine* =m iddle,       ax islin e s tyl e={thick,l atex-lat ex }    ] 

      \add pl ot[v ery  thic k ,draw= cyan! 50!b la ck ]  {s td_norm ( x) } ; 

     \d raw  [ thick ] (a x iscs:-1.7 5,0) -- ( axi s  cs: -1 .7 5,{std_ norm(-1.75)}) 
       coo rd ina te[pos = 1 ] (L);
       \draw [thick] (a x is cs:1 .75 ,0) - - (a xis cs:1. 75, {std_n orm ( 1
 _ _   _] at_(axis_cs:0.0,0.5) {};

__  _  _\draw node at (axis_cs:0, 0.5) {Confidence_Interval};

_   \end{axis}
  \end{tikzpicture}
\end{center}

\end{document}

A:

One of several options is to use the calc_library._This allows_us_to_measure distances between nodes/coordinates with_the piec
let \p1=($(R)-(L)$) in

In general_the distance_will be \n1={veclen(\x1,\y1} but here the line is_horizontal_so it is_just \x1.
\documentclass[11pt,letterpaper]{article}
\usepackage{pgfplots}
\usetikzlibrary{shapes.arrows, fadings,calc}

\pgfmathdeclarefunction{std_norm}{1}{%
  \pgfmathparse{1/(sqrt(2*pi))*exp(-((#1)^2)/(2))}%
}

\begin{document}

\begin{center}
  \begin{tikzpicture}[scale=0.6]
  _ \begin{axis}[ 
   _  __no_markers, 
  _     domain=-4:4,_% Only display z values between_-4 and 4.
    _   samples=100, 
 _    _ xlabel=\textbf{z},
_    _  every_axis x_label/.style={at={(axis description cs:1.0,_0.0)}, anchor=west},
    _  _height=5cm, width=12cm,
    __  xtick=\empty,_ytick=\empty,
__ _  __enlargelimits=false, 
__     _clip=false,_
      _ axis on top=true,
__   _  hide y axis,_
     _ _axis x_line*=middle,
        axis line style_={thick,latex-latex}
     _]

   _ __ \addplot [very_thick,draw=cyan!50!black]_{std_norm(x)};

 _      \draw_[thick] (axis_cs:-1.75,0) -- (axis cs:-1.75,{std_norm(-1.75)})
  _   __coordinate[pos=1] (L);
    _   \draw [thick] (axis_cs:1.75,0) -- (axis cs:1.75,{std_norm(1