DOC: stats: Add Examples for bartlett, fligner, levene. (#11880)
DOC: stats: Add Examples for bartlett, fligner, levene. (#11880)

* DOC: stats: Add Examples for bartlett, fligner, levene.

* DOC: stats: Update Examples for bartlett, fligner and levene.

Show the variances of the datasets used in the example.
andyfaff/scipy,scipy/scipy,grlee77/scipy,perimosocordiae/scipy,anntzer/scipy,perimosocordiae/scipy,WarrenWeckesser/scipy,scipy/scipy,tylerjereddy/scipy,perimosocordiae/scipy,nmayorov/scipy,mdhaber/scipy,vigna/scipy,zerothi/scipy,grlee77/scipy,endolith/scipy,perimosocordiae/scipy,rgommers/scipy,endolith/scipy,perimosocordiae/scipy,ilayn/scipy,Stefan-Endres/scipy,zerothi/scipy,WarrenWeckesser/scipy,zerothi/scipy,rgommers/scipy,pizzathief/scipy,person142/scipy,Stefan-Endres/scipy,pizzathief/scipy,scipy/scipy,endolith/scipy,endolith/scipy,ilayn/scipy,nmayorov/scipy,tylerjereddy/scipy,e-q/scipy,ilayn/scipy,mdhaber/scipy,ilayn/scipy,e-q/scipy,Eric89GXL/scipy,zerothi/scipy,rgommers/scipy,Stefan-Endres/scipy,matthew-brett/scipy,mdhaber/scipy,andyfaff/scipy,grlee77/scipy,e-q/scipy,mdhaber/scipy,tylerjereddy/scipy,pizzathief/scipy,anntzer/scipy,vigna/scipy,Eric89GXL/scipy,vigna/scipy,matthew-brett/scipy,grlee77/scipy,tylerjereddy/scipy,mdhaber/scipy,matthew-brett/scipy,WarrenWeckesser/scipy,anntzer/scipy,zerothi/scipy,Stefan-Endres/scipy,person142/scipy,scipy/scipy,person142/scipy,WarrenWeckesser/scipy,rgommers/scipy,e-q/scipy,rgommers/scipy,Eric89GXL/scipy,person142/scipy,matthew-brett/scipy,endolith/scipy,nmayorov/scipy,nmayorov/scipy,grlee77/scipy,andyfaff/scipy,zerothi/scipy,vigna/scipy,andyfaff/scipy,tylerjereddy/scipy,vigna/scipy,matthew-brett/scipy,anntzer/scipy,Stefan-Endres/scipy,endolith/scipy,person142/scipy,nmayorov/scipy,WarrenWeckesser/scipy,pizzathief/scipy,Eric89GXL/scipy,scipy/scipy,anntzer/scipy,andyfaff/scipy,mdhaber/scipy,pizzathief/scipy,WarrenWeckesser/scipy,ilayn/scipy,e-q/scipy,Eric89GXL/scipy,Stefan-Endres/scipy,anntzer/scipy,Eric89GXL/scipy,perimosocordiae/scipy,ilayn/scipy,andyfaff/scipy,scipy/scipy