{"id":3584,"date":"2023-07-16T17:05:04","date_gmt":"2023-07-16T17:05:04","guid":{"rendered":"https:\/\/statorials.org\/pt\/como-ler-um-boxplot-com-outliers\/"},"modified":"2023-07-16T17:05:04","modified_gmt":"2023-07-16T17:05:04","slug":"como-ler-um-boxplot-com-outliers","status":"publish","type":"post","link":"https:\/\/statorials.org\/pt\/como-ler-um-boxplot-com-outliers\/","title":{"rendered":"Como ler um box plot com outliers (com exemplo)"},"content":{"rendered":"<p><\/p>\n<hr>\n<p><span style=\"color: #000000;\">Um <strong>box plot<\/strong> \u00e9 um tipo de gr\u00e1fico que exibe o resumo de cinco d\u00edgitos de um conjunto de dados, que inclui:<\/span><\/p>\n<ul>\n<li> <span style=\"color: #000000;\">O valor m\u00ednimo<\/span><\/li>\n<li> <span style=\"color: #000000;\">O primeiro quartil (o 25\u00ba percentil)<\/span><\/li>\n<li> <span style=\"color: #000000;\">O valor mediano<\/span><\/li>\n<li> <span style=\"color: #000000;\">O terceiro quartil (o 75\u00ba percentil)<\/span><\/li>\n<li> <span style=\"color: #000000;\">O valor m\u00e1ximo<\/span><\/li>\n<\/ul>\n<p> <span style=\"color: #000000;\">Para fazer um box plot, primeiro desenhamos uma caixa do primeiro ao terceiro quartil.<\/span><\/p>\n<p> <span style=\"color: #000000;\">A seguir, tra\u00e7amos uma linha vertical na mediana.<\/span><\/p>\n<p> <span style=\"color: #000000;\">Por fim, tra\u00e7amos \u201cbigodes\u201d dos quartis at\u00e9 o valor m\u00ednimo e m\u00e1ximo.<\/span> <\/p>\n<p><img decoding=\"async\" loading=\"lazy\" class=\" wp-image-29584 aligncenter\" src=\"https:\/\/statorials.org\/wp-content\/uploads\/2023\/08\/boite-aberrante1.jpg\" alt=\"\" width=\"424\" height=\"122\" srcset=\"\" sizes=\"auto, \"><\/p>\n<p> <span style=\"color: #000000;\">Na maioria dos softwares estat\u00edsticos, uma observa\u00e7\u00e3o<\/span> <span style=\"color: #000000;\">\u00e9 definida como discrepante se atender a um dos dois requisitos a seguir:<\/span><\/p>\n<ul>\n<li> <span style=\"color: #000000;\">A observa\u00e7\u00e3o \u00e9 1,5 vezes o intervalo interquartil abaixo do primeiro quartil (Q1)<\/span><\/li>\n<li> <span style=\"color: #000000;\">A observa\u00e7\u00e3o \u00e9 1,5 vezes o intervalo interquartil acima do terceiro quartil (Q3).<\/span><\/li>\n<\/ul>\n<p> <span style=\"color: #000000;\">Se existir um valor discrepante em um conjunto de dados, ele geralmente ser\u00e1 rotulado com um pequeno ponto fora da faixa de bigodes no gr\u00e1fico de caixa:<\/span> <\/p>\n<p><img decoding=\"async\" loading=\"lazy\" class=\"aligncenter wp-image-29585\" src=\"https:\/\/statorials.org\/wp-content\/uploads\/2023\/08\/boite-aberrante2.jpg\" alt=\"como ler outliers em boxplots\" width=\"523\" height=\"178\" srcset=\"\" sizes=\"auto, \"><\/p>\n<p> <span style=\"color: #000000;\">Quando isso acontece, aos valores \u201cm\u00ednimo\u201d e \u201cm\u00e1ximo\u201d no boxplot s\u00e3o simplesmente atribu\u00eddos os valores de Q1 \u2013 1,5*IQR e Q3 + 1,5*IQR, respectivamente.<\/span><\/p>\n<p> <span style=\"color: #000000;\">O exemplo a seguir mostra como interpretar gr\u00e1ficos de caixa com e sem valores discrepantes.<\/span><\/p>\n<h2> <span style=\"color: #000000;\"><strong>Exemplo: Interpretando um Box Plot com Outliers<\/strong><\/span><\/h2>\n<p> <span style=\"color: #000000;\">Suponha que criemos os dois box plots a seguir para visualizar a distribui\u00e7\u00e3o de pontos marcados por jogadores de basquete de dois times diferentes:<\/span> <\/p>\n<p><img decoding=\"async\" loading=\"lazy\" class=\" wp-image-29586 aligncenter\" src=\"https:\/\/statorials.org\/wp-content\/uploads\/2023\/08\/boite-aberrante3.jpg\" alt=\"\" width=\"504\" height=\"432\" srcset=\"\" sizes=\"auto, \"><\/p>\n<p> <span style=\"color: #000000;\">O boxplot esquerdo para o Time A n\u00e3o tem valores discrepantes, pois n\u00e3o h\u00e1 pequenos pontos localizados fora do bigode m\u00ednimo ou m\u00e1ximo.<\/span><\/p>\n<p> <span style=\"color: #000000;\">No entanto, o boxplot certo para a Equipe B tem um valor discrepante acima do valor \u201cm\u00e1ximo\u201d e um valor discrepante abaixo do valor \u201cm\u00ednimo\u201d.<\/span><\/p>\n<p> <span style=\"color: #000000;\">Aqui est\u00e1 o resumo atual de cinco d\u00edgitos para a distribui\u00e7\u00e3o da vari\u00e1vel \u201cPontos\u201d para a Equipe B:<\/span><\/p>\n<ul>\n<li> <span style=\"color: #000000;\">Valor m\u00ednimo: 1,1<\/span><\/li>\n<li> <span style=\"color: #000000;\">Primeiro quartil: 10,5<\/span><\/li>\n<li> <span style=\"color: #000000;\">Mediana: 12,7<\/span><\/li>\n<li> <span style=\"color: #000000;\">Terceiro quartil: 15,6<\/span><\/li>\n<li> <span style=\"color: #000000;\">Valor m\u00e1ximo: 23,5<\/span><\/li>\n<\/ul>\n<p> <span style=\"color: #000000;\">Veja como calcular os limites de poss\u00edveis valores discrepantes:<\/span><\/p>\n<p> <span style=\"color: #000000;\"><strong>Escala interquartil<\/strong> : Terceiro quartil \u2013 Primeiro quartil = 15,6 \u2013 10,5 = 5,1<\/span><\/p>\n<p> <span style=\"color: #000000;\"><strong>Limite inferior<\/strong> : Q1 \u2013 1,5*IQR = 10,5 \u2013 1,5*5,1 = 2,85<\/span><\/p>\n<p> <span style=\"color: #000000;\"><strong>Limite superior<\/strong> : Q3 + 1,5*IQR = 15,6 + 1,5*5,1 = 23,25<\/span><\/p>\n<p> <span style=\"color: #000000;\">Os bigodes para os valores m\u00ednimo e m\u00e1ximo no boxplot s\u00e3o colocados em <strong>2,85<\/strong> e <strong>23,25<\/strong> .<\/span><\/p>\n<p> <span style=\"color: #000000;\">Assim, observa\u00e7\u00f5es com valores de <strong>1,1<\/strong> e <strong>23,5<\/strong> se qualificam como valores discrepantes no boxplot porque est\u00e3o fora dos limites inferior e superior.<\/span><\/p>\n<p> <span style=\"color: #000000;\"><strong>B\u00f4nus<\/strong> : aqui est\u00e1 o c\u00f3digo exato que usamos para criar esses dois boxplots na linguagem de programa\u00e7\u00e3o R:<\/span><\/p>\n<pre style=\"background-color: #ececec; font-size: 15px;\"> <strong><span style=\"color: #008000;\">library<\/span> (ggplot2)\n\n<span style=\"color: #008080;\">#make this example reproducible \n<\/span>set. <span style=\"color: #3366ff;\">seeds<\/span> (2)\n\n<span style=\"color: #008080;\">#create data frame\n<\/span>df &lt;- data. <span style=\"color: #3366ff;\">frame<\/span> (Team = factor(rep(c(\"A\", \"B\"), each = 200)), \n                 Points = c(rnorm(200, mean = 15, sd = 3), \n                           rnorm(200, mean = 12, sd = 4))) \n\n<span style=\"color: #008080;\">#create box plots\n<\/span>ggplot(df, aes(x = Team, y = Points)) +\n  stat_boxplot(geom = \" <span style=\"color: #ff0000;\">errorbar<\/span> \", width = 0.5) +  \n  geom_boxplot() \n\n<span style=\"color: #008080;\">#calculate summary statistics for each team\n<\/span>tapply(df$Points, df$Team, summary)\n<\/strong><\/pre>\n<h2> <span style=\"color: #000000;\"><strong>Recursos adicionais<\/strong><\/span><\/h2>\n<p> <span style=\"color: #000000;\">Os tutoriais a seguir fornecem informa\u00e7\u00f5es adicionais sobre box plots:<\/span><\/p>\n<p> <a href=\"https:\/\/statorials.org\/pt\/comparar-boxplots\/\" target=\"_blank\" rel=\"noopener\">Como comparar gr\u00e1ficos de caixa<\/a><br \/> <a href=\"https:\/\/statorials.org\/pt\/simetria-do-boxplot\/\" target=\"_blank\" rel=\"noopener\">Como identificar assimetria em box plots<\/a><br \/> <a href=\"https:\/\/statorials.org\/pt\/como-encontrar-o-iqr-do-box-plot\/\" target=\"_blank\" rel=\"noopener\">Como encontrar o intervalo interquartil de um boxplot<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Um box plot \u00e9 um tipo de gr\u00e1fico que exibe o resumo de cinco d\u00edgitos de um conjunto de dados, que inclui: O valor m\u00ednimo O primeiro quartil (o 25\u00ba percentil) O valor mediano O terceiro quartil (o 75\u00ba percentil) O valor m\u00e1ximo Para fazer um box plot, primeiro desenhamos uma caixa do primeiro ao [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11],"tags":[],"class_list":["post-3584","post","type-post","status-publish","format-standard","hentry","category-guia"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v21.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Como ler um box plot com outliers (com exemplo) - Statorials<\/title>\n<meta name=\"description\" content=\"Este tutorial explica como ler um boxplot com outliers, com um exemplo.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/statorials.org\/pt\/como-ler-um-boxplot-com-outliers\/\" \/>\n<meta property=\"og:locale\" content=\"pt_PT\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" 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