Which one of the following is CORRECT?
1
\({\rm{PE}}\,{\rm{ = }}\,\frac{{.6475\left( {1\, - \,{{\rm{r}}^2}} \right)}}{{\sqrt {\rm{n}} }}\)
2
\({\rm{PE}}\,{\rm{ = }}\,\frac{{.6745\left( {1\, - \,{{\rm{r}}^2}} \right)}}{{\sqrt {\rm{n}} }}\)
3
\({\rm{PE}}\,{\rm{ = }}\,\frac{{.6475\sqrt {\rm{n}} }}{{1\, - \,{{\rm{r}}^2}}}\)
4
\({\rm{PE}}\,{\rm{ = }}\,\frac{{{\rm{.6475}}\left( {{\rm{1}}\,{\rm{ - }}\,{{\rm{r}}^{\rm{2}}}} \right)}}{{\rm{n}}}\)