{"id":4504,"date":"2023-07-10T14:11:32","date_gmt":"2023-07-10T14:11:32","guid":{"rendered":"https:\/\/statorials.org\/pt\/wald-teste-python\/"},"modified":"2023-07-10T14:11:32","modified_gmt":"2023-07-10T14:11:32","slug":"wald-teste-python","status":"publish","type":"post","link":"https:\/\/statorials.org\/pt\/wald-teste-python\/","title":{"rendered":"Como realizar um teste wald em python"},"content":{"rendered":"<p><\/p>\n<hr>\n<p><span style=\"color: #000000;\">Um <strong>teste de Wald<\/strong> pode ser usado para testar se um ou mais par\u00e2metros de um modelo s\u00e3o iguais a determinados valores.<\/span><\/p>\n<p> <span style=\"color: #000000;\">Este teste \u00e9 frequentemente usado para determinar se uma ou mais vari\u00e1veis preditoras em um modelo de regress\u00e3o s\u00e3o iguais a zero.<\/span><\/p>\n<p> <span style=\"color: #000000;\">Usamos as seguintes <a href=\"https:\/\/statorials.org\/pt\/teste-de-hipotese-1\/\" target=\"_blank\" rel=\"noopener\">hip\u00f3teses<\/a> nulas e alternativas para este teste:<\/span><\/p>\n<ul>\n<li> <span style=\"color: #000000;\"><strong>H <sub>0<\/sub><\/strong> : Alguns conjuntos de vari\u00e1veis preditoras s\u00e3o todos iguais a zero.<\/span><\/li>\n<li> <span style=\"color: #000000;\"><strong><sub>HA<\/sub><\/strong> : Nem todas as vari\u00e1veis preditoras no conjunto s\u00e3o iguais a zero.<\/span><\/li>\n<\/ul>\n<p> <span style=\"color: #000000;\">Se n\u00e3o conseguirmos rejeitar a hip\u00f3tese nula, poderemos remover o conjunto especificado de vari\u00e1veis preditoras do modelo, pois elas n\u00e3o fornecem uma melhoria estatisticamente significativa no ajuste do modelo.<\/span><\/p>\n<p> <span style=\"color: #000000;\">O exemplo a seguir mostra como realizar um teste Wald em Python<\/span><\/p>\n<h2> <span style=\"color: #000000;\"><strong>Exemplo: teste Wald em Python<\/strong><\/span><\/h2>\n<p> <span style=\"color: #000000;\">Para este exemplo, usaremos o famoso conjunto de dados <strong>mtcars<\/strong> para ajustar o seguinte modelo de regress\u00e3o linear m\u00faltipla:<\/span><\/p>\n<p> <span style=\"color: #000000;\">mpg = \u03b2 <sub>0<\/sub> + \u03b2 <sub>1<\/sub> dispon\u00edvel + \u03b2 <sub>2<\/sub> carb + \u03b2 <sub>3<\/sub> cv + \u03b2 <sub>4<\/sub> cilindros<\/span><\/p>\n<p> <span style=\"color: #000000;\">O c\u00f3digo a seguir mostra como ajustar esse modelo de regress\u00e3o e exibir o resumo do modelo:<\/span><\/p>\n<pre style=\"background-color: #ececec; font-size: 15px;\"> <strong><span style=\"color: #008000;\">import<\/span> statsmodels. <span style=\"color: #3366ff;\">formula<\/span> . <span style=\"color: #3366ff;\">api<\/span> <span style=\"color: #008000;\">as<\/span> smf\n<span style=\"color: #008000;\">import<\/span> pandas <span style=\"color: #008000;\">as<\/span> pd\n<span style=\"color: #008000;\">import<\/span> io\n\n<span style=\"color: #008080;\">#define dataset as string\n<\/span>mtcars_data=\"\"\"model,mpg,cyl,disp,hp,drat,wt,qsec,vs,am,gear,carb\nMazda RX4,21,6,160,110,3.9,2.62,16.46,0,1,4,4\nMazda RX4 Wag,21.6,160,110,3.9,2.875,17.02,0,1,4,4\nDatsun 710,22.8,4,108,93,3.85,2.32,18.61,1,1,4,1\nHornet 4 Drive,21.4,6,258,110,3.08,3.215,19.44,1,0,3,1\nHornet Sportabout,18.7,8,360,175,3.15,3.44,17.02,0,0,3,2\nValiant,18.1,6,225,105,2.76,3.46,20.22,1,0,3,1\nDuster 360,14.3,8,360,245,3.21,3.57,15.84,0,0,3,4\nMerc 240D,24.4,4,146.7,62,3.69,3.19,20,1,0,4,2\nMerc 230,22.8,4,140.8,95,3.92,3.15,22.9,1,0,4,2\nMerc 280,19.2,6,167.6,123,3.92,3.44,18.3,1,0,4,4\nMerc 280C,17.8,6,167.6,123,3.92,3.44,18.9,1,0,4,4\nMerc 450SE,16.4,8,275.8,180,3.07,4.07,17.4,0,0,3,3\nMerc 450SL,17.3,8,275.8,180,3.07,3.73,17.6,0,0,3,3\nMerc 450SLC,15.2,8,275.8,180,3.07,3.78,18,0,0,3,3\nCadillac Fleetwood,10.4,8,472,205,2.93,5.25,17.98,0,0,3,4\nLincoln Continental,10.4,8,460,215,3,5.424,17.82,0,0,3,4\nChrysler Imperial,14.7,8,440,230,3.23,5.345,17.42,0,0,3,4\nFiat 128,32.4,4,78.7,66,4.08,2.2,19.47,1,1,4,1\nHonda Civic,30.4,4,75.7,52,4.93,1.615,18.52,1,1,4,2\nToyota Corolla,33.9,4,71.1,65,4.22,1.835,19.9,1,1,4,1\nToyota Corona,21.5,4,120.1,97,3.7,2.465,20.01,1,0,3,1\nDodge Challenger,15.5,8,318,150,2.76,3.52,16.87,0,0,3,2\nAMC Javelin,15.2,8,304,150,3.15,3.435,17.3,0,0,3,2\nCamaro Z28,13.3,8,350,245,3.73,3.84,15.41,0,0,3,4\nPontiac Firebird,19.2,8,400,175,3.08,3.845,17.05,0,0,3,2\nFiat X1-9,27.3,4,79,66,4.08,1.935,18.9,1,1,4,1\nPorsche 914-2,26,4,120.3,91,4.43,2.14,16.7,0,1,5,2\nLotus Europa,30.4,4,95.1,113,3.77,1.513,16.9,1,1,5,2\nFord Pantera L,15.8,8,351,264,4.22,3.17,14.5,0,1,5,4\nFerrari Dino,19.7,6,145,175,3.62,2.77,15.5,0,1,5,6\nMaserati Bora,15.8,301,335,3.54,3.57,14.6,0,1,5,8\nVolvo 142E,21.4,4,121,109,4.11,2.78,18.6,1,1,4,2\"\"\"\n\n<span style=\"color: #008080;\">#convert string to DataFrame\n<\/span>df = pd. <span style=\"color: #3366ff;\">read_csv<\/span> ( <span style=\"color: #3366ff;\">io.StringIO<\/span> (mtcars_data), sep=\" <span style=\"color: #ff0000;\">,<\/span> \")\n\n<span style=\"color: #008080;\">#fit multiple linear regression model\n<\/span>results = smf. <span style=\"color: #3366ff;\">ols<\/span> (' <span style=\"color: #ff0000;\">mpg~disp+carb+hp+cyl<\/span> ',df). <span style=\"color: #3366ff;\">fit<\/span> ()\n\n<span style=\"color: #008080;\">#view regression model summary\n<\/span>results. <span style=\"color: #3366ff;\">summary<\/span> ()\n\n\tcoef std err t P&gt;|t| [0.025 0.975]\nIntercept34.0216 2.523 13.482 0.000 28.844 39.199\navailable -0.0269 0.011 -2.379 0.025 -0.050 -0.004\ncarb -0.9269 0.579 -1.601 0.121 -2.115 0.261\nhp 0.0093 0.021 0.452 0.655 -0.033 0.052\ncyl -1.0485 0.784 -1.338 0.192 -2.657 0.560\n<\/strong><\/pre>\n<p> <span style=\"color: #000000;\">A seguir, podemos usar a fun\u00e7\u00e3o <strong>wald_test()<\/strong> <strong>do statsmodels<\/strong> para testar se os coeficientes de regress\u00e3o para as vari\u00e1veis preditoras &#8220;hp&#8221; e &#8220;cyl&#8221; s\u00e3o ambos iguais a zero.<\/span><\/p>\n<p> <span style=\"color: #000000;\">O c\u00f3digo a seguir mostra como usar esta fun\u00e7\u00e3o na pr\u00e1tica:<\/span><\/p>\n<pre style=\"background-color: #ececec; font-size: 15px;\"> <strong><span style=\"color: #008080;\">#perform Wald Test to determine if 'hp' and 'cyl' coefficients are both zero<\/span>\n<span style=\"color: #008000;\">print<\/span> ( <span style=\"color: #3366ff;\">results.wald_test<\/span> (' <span style=\"color: #ff0000;\">(hp=0, cyl=0)<\/span> '))\n\nF test: F=array([[0.91125429]]), p=0.41403001184235005, df_denom=27, df_num=2\n<\/strong><\/pre>\n<p> <span style=\"color: #000000;\">Pelo resultado, podemos ver que o <a href=\"https:\/\/statorials.org\/pt\/p-valores-significancia-estatistica\/\" target=\"_blank\" rel=\"noopener\">valor p<\/a> do teste \u00e9 <strong>0,414<\/strong> .<\/span><\/p>\n<p> <span style=\"color: #000000;\">Como este valor p n\u00e3o \u00e9 inferior a 0,05, n\u00e3o rejeitamos a hip\u00f3tese nula do teste de Wald.<\/span><\/p>\n<p> <span style=\"color: #000000;\">Isso significa que podemos assumir que os coeficientes de regress\u00e3o para as vari\u00e1veis preditoras \u201chp\u201d e \u201ccil\u201d s\u00e3o ambos iguais a zero.<\/span><\/p>\n<p> <span style=\"color: #000000;\">Podemos remover esses termos do modelo porque eles n\u00e3o melhoram estatisticamente significativamente o ajuste geral do modelo.<\/span><\/p>\n<h2> <span style=\"color: #000000;\"><strong>Recursos adicionais<\/strong><\/span><\/h2>\n<p> <span style=\"color: #000000;\">Os tutoriais a seguir explicam como realizar outras opera\u00e7\u00f5es comuns em Python:<\/span><\/p>\n<p> <span style=\"color: #000000;\"><a href=\"https:\/\/statorials.org\/pt\/regressao-linear-simples-em-python\/\" target=\"_blank\" rel=\"noopener\">Como realizar regress\u00e3o linear simples<\/a><br \/> <a href=\"https:\/\/statorials.org\/pt\/regressao-polinomial-python\/\" target=\"_blank\" rel=\"noopener\">Como realizar regress\u00e3o polinomial em Python<\/a><br \/> <a href=\"https:\/\/statorials.org\/pt\/como-calcular-vive-em-python\/\" target=\"_blank\" rel=\"noopener\">Como calcular VIF em Python<\/a><\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Um teste de Wald pode ser usado para testar se um ou mais par\u00e2metros de um modelo s\u00e3o iguais a determinados valores. Este teste \u00e9 frequentemente usado para determinar se uma ou mais vari\u00e1veis preditoras em um modelo de regress\u00e3o s\u00e3o iguais a zero. Usamos as seguintes hip\u00f3teses nulas e alternativas para este teste: H [&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-4504","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 realizar um teste Wald em Python \u2013 Estatologia<\/title>\n<meta name=\"description\" content=\"Este tutorial explica como realizar um teste Wald em Python, incluindo um exemplo completo.\" \/>\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\/wald-teste-python\/\" \/>\n<meta property=\"og:locale\" content=\"pt_PT\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Como realizar um teste Wald em Python \u2013 Estatologia\" \/>\n<meta property=\"og:description\" content=\"Este tutorial explica como realizar um teste Wald em Python, incluindo um exemplo completo.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/statorials.org\/pt\/wald-teste-python\/\" \/>\n<meta property=\"og:site_name\" content=\"Statorials\" \/>\n<meta property=\"article:published_time\" content=\"2023-07-10T14:11:32+00:00\" \/>\n<meta name=\"author\" content=\"Dr. benjamim anderson\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Escrito por\" \/>\n\t<meta name=\"twitter:data1\" content=\"Dr. benjamim anderson\" \/>\n\t<meta name=\"twitter:label2\" content=\"Tempo estimado de leitura\" \/>\n\t<meta name=\"twitter:data2\" content=\"3 minutos\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/statorials.org\/pt\/wald-teste-python\/\",\"url\":\"https:\/\/statorials.org\/pt\/wald-teste-python\/\",\"name\":\"Como realizar um teste Wald em Python \u2013 Estatologia\",\"isPartOf\":{\"@id\":\"https:\/\/statorials.org\/pt\/#website\"},\"datePublished\":\"2023-07-10T14:11:32+00:00\",\"dateModified\":\"2023-07-10T14:11:32+00:00\",\"author\":{\"@id\":\"https:\/\/statorials.org\/pt\/#\/schema\/person\/e08f98e8db95e0aa9c310e1b27c9c666\"},\"description\":\"Este tutorial explica como realizar um teste Wald em Python, incluindo um exemplo completo.\",\"breadcrumb\":{\"@id\":\"https:\/\/statorials.org\/pt\/wald-teste-python\/#breadcrumb\"},\"inLanguage\":\"pt-PT\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/statorials.org\/pt\/wald-teste-python\/\"]}]},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/statorials.org\/pt\/wald-teste-python\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Lar\",\"item\":\"https:\/\/statorials.org\/pt\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Como realizar um teste wald em python\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/statorials.org\/pt\/#website\",\"url\":\"https:\/\/statorials.org\/pt\/\",\"name\":\"Statorials\",\"description\":\"O seu guia para a literacia estat\u00edstica!\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/statorials.org\/pt\/?s={search_term_string}\"},\"query-input\":\"required name=search_term_string\"}],\"inLanguage\":\"pt-PT\"},{\"@type\":\"Person\",\"@id\":\"https:\/\/statorials.org\/pt\/#\/schema\/person\/e08f98e8db95e0aa9c310e1b27c9c666\",\"name\":\"Dr. benjamim anderson\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"pt-PT\",\"@id\":\"https:\/\/statorials.org\/pt\/#\/schema\/person\/image\/\",\"url\":\"https:\/\/statorials.org\/pt\/wp-content\/uploads\/2023\/10\/Dr.-Benjamin-Anderson-96x96.jpg\",\"contentUrl\":\"https:\/\/statorials.org\/pt\/wp-content\/uploads\/2023\/10\/Dr.-Benjamin-Anderson-96x96.jpg\",\"caption\":\"Dr. benjamim anderson\"},\"description\":\"Ol\u00e1, sou Benjamin, um professor aposentado de estat\u00edstica que se tornou professor dedicado na Statorials. 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