{"id":222,"date":"2026-10-03T18:01:29","date_gmt":"2026-10-03T17:01:29","guid":{"rendered":"https:\/\/wpcalc.com\/pt\/calculadora-intervalo-de-confianca\/"},"modified":"2026-10-03T18:01:29","modified_gmt":"2026-10-03T17:01:29","slug":"calculadora-intervalo-de-confianca","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/pt\/estatistica\/calculadora-intervalo-de-confianca\/","title":{"rendered":"Calculadora de Intervalo de Confian\u00e7a"},"content":{"rendered":"<section class=\"not-prose calculator-box\" aria-labelledby=\"calculator-title\"><div class=\"flex items-baseline sm:items-center justify-between gap-2 sm:gap-3\"><div class=\"flex flex-col sm:flex-row sm:items-center gap-2\"><span class=\"icon icon-calculator text-primary-700! text-base! dark:text-primary-300!\" aria-hidden=\"true\"><\/span><h2 id=\"calculator-title\" class=\"text-lg font-display font-bold\">Calcular um intervalo de confian\u00e7a<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"222\" data-favorite-title=\"Intervalo de Confian\u00e7a\" data-favorite-url=\"https:\/\/wpcalc.com\/pt\/estatistica\/calculadora-intervalo-de-confianca\/\" data-favorite-excerpt=\"Calcule um intervalo de confian\u00e7a para uma m\u00e9dia ou propor\u00e7\u00e3o populacional. Insira as estat\u00edsticas da sua amostra, escolha um n\u00edvel de confian\u00e7a e obtenha a margem de erro e os limites inferior e superior.\" aria-label=\"Adicionar aos favoritos\" data-favorite-icon=\"icon icon-wpcalc-sample-size\">\n    <span class=\"icon icon-shape-star-empty\" aria-hidden=\"true\"><\/span>\n  <\/button>\n  <div class=\"calcdash-favorite__tip\" aria-hidden=\"true\">\n   <span class=\"favorite-tooltip\" id=\"favorite-tooltip\"><\/span>\n  <\/div>\n  <span class=\"sr-only\" role=\"status\" id=\"favorite-status\"><\/span>\n<\/div><\/div><form action=\"https:\/\/wpcalc.com\/pt\/estatistica\/calculadora-intervalo-de-confianca\/\" method=\"POST\" class=\"calculator\" id=\"calculator-222\" data-post=\"222\"><fieldset class=\"fieldset-input is-1\"><legend class=\"sr-only\">Campos de entrada<\/legend><div class=\"field\" id=\"input-1\"><label for=\"field-1\">Tipo de estimativa<\/label><div class=\"grid grid-cols-1\"><select id=\"field-1\" name=\"tipo_de_estimativa\"><option value=\"mean\" selected>M\u00e9dia amostral<\/option><option value=\"prop\">Propor\u00e7\u00e3o amostral<\/option><\/select><svg class=\"pointer-events-none col-start-1 row-start-1 mr-2 size-5 self-center justify-self-end text-gray-500 sm:size-4\" viewBox=\"0 0 16 16\" fill=\"currentColor\" aria-hidden=\"true\" data-slot=\"icon\">\n              <path fill-rule=\"evenodd\" d=\"M4.22 6.22a.75.75 0 0 1 1.06 0L8 8.94l2.72-2.72a.75.75 0 1 1 1.06 1.06l-3.25 3.25a.75.75 0 0 1-1.06 0L4.22 7.28a.75.75 0 0 1 0-1.06Z\" clip-rule=\"evenodd\" \/>\n            <\/svg><\/div><\/div><div class=\"field has-term\" id=\"input-2\"><label for=\"field-2\">M\u00e9dia amostral (x\u0304)<\/label><div class=\"term\">x\u0304<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"number\" name=\"mdia_amostral_x\" id=\"field-2\" aria-describedby=\"calc-info-2\" placeholder=\"e.g. 100\" step=\"any\" value=\"100\"\/><small id=\"calc-info-2\">Para uma propor\u00e7\u00e3o, insira a propor\u00e7\u00e3o amostral em formato decimal, por exemplo, 0,55 para 55%.<\/small><\/div><div class=\"field has-term\" id=\"input-3\" hidden><label for=\"field-3\">Desvio padr\u00e3o amostral (s)<\/label><div class=\"term\">s<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"desvio_padro_amostral_s\" id=\"field-3\" aria-describedby=\"calc-info-3\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 15\" min=\"0\" value=\"15\"\/><small id=\"calc-info-3\">Desvio padr\u00e3o amostral dos dados. Deve ser maior que 0. N\u00e3o \u00e9 usado para propor\u00e7\u00f5es.<\/small><\/div><div class=\"field has-term\" id=\"input-4\"><label for=\"field-4\">Tamanho da amostra (n)<\/label><div class=\"term\">n<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"tamanho_da_amostra_n\" id=\"field-4\" aria-describedby=\"calc-info-4\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 25\" min=\"2\" value=\"25\"\/><small id=\"calc-info-4\">N\u00famero de observa\u00e7\u00f5es. Deve ser um n\u00famero inteiro de pelo menos 2.<\/small><\/div><div class=\"field\" id=\"input-5\"><label for=\"field-5\">N\u00edvel de confian\u00e7a<\/label><div class=\"grid grid-cols-1\"><select id=\"field-5\" name=\"nvel_de_confiana\"><option value=\"80\">80%<\/option><option value=\"90\">90%<\/option><option value=\"95\" selected>95%<\/option><option value=\"98\">98%<\/option><option value=\"99\">99%<\/option><option value=\"99.9\">99.9%<\/option><\/select><svg class=\"pointer-events-none col-start-1 row-start-1 mr-2 size-5 self-center justify-self-end text-gray-500 sm:size-4\" viewBox=\"0 0 16 16\" fill=\"currentColor\" aria-hidden=\"true\" data-slot=\"icon\">\n              <path fill-rule=\"evenodd\" d=\"M4.22 6.22a.75.75 0 0 1 1.06 0L8 8.94l2.72-2.72a.75.75 0 1 1 1.06 1.06l-3.25 3.25a.75.75 0 0 1-1.06 0L4.22 7.28a.75.75 0 0 1 0-1.06Z\" clip-rule=\"evenodd\" \/>\n            <\/svg><\/div><\/div><div class=\"field\" id=\"input-6\"><label for=\"field-6\">M\u00e9todo do valor cr\u00edtico<\/label><div class=\"grid grid-cols-1\"><select id=\"field-6\" name=\"mtodo_do_valor_crtico\"><option value=\"auto\" selected>Autom\u00e1tico (t quando n &lt; 30, z quando n \u2265 30)<\/option><option value=\"t\">t de Student (n \u2212 1 graus de liberdade)<\/option><option value=\"z\">z normal (use quando \u03c3 \u00e9 conhecido)<\/option><\/select><svg class=\"pointer-events-none col-start-1 row-start-1 mr-2 size-5 self-center justify-self-end text-gray-500 sm:size-4\" viewBox=\"0 0 16 16\" fill=\"currentColor\" aria-hidden=\"true\" data-slot=\"icon\">\n              <path fill-rule=\"evenodd\" d=\"M4.22 6.22a.75.75 0 0 1 1.06 0L8 8.94l2.72-2.72a.75.75 0 1 1 1.06 1.06l-3.25 3.25a.75.75 0 0 1-1.06 0L4.22 7.28a.75.75 0 0 1 0-1.06Z\" clip-rule=\"evenodd\" \/>\n            <\/svg><\/div><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Recalcular\" id=\"calculate-button\" data-post=\"222\">Calcular<\/button><button type=\"reset\">Redefinir<\/button><\/div><div class=\"field is-checkbox hidden!\" id=\"field-auto-calc\"><input type=\"checkbox\" id=\"auto-calc\"><label for=\"auto-calc\">Calcular automaticamente<\/label><small>Se ativado, o resultado \u00e9 atualizado automaticamente quando voc\u00ea altera qualquer valor.<\/small><\/div><div class=\"fieldset-result is-hidden\" aria-labelledby=\"result-title\" aria-live=\"polite\" role=\"region\"> <h3 class=\"result-title bg-gradient-to-r from-primary-50 to-gray-50 dark:from-primary-900 dark:to-gray-800\" id=\"result-title\"><span class=\"icon icon-s-pulse\" aria-hidden=\"true\"><\/span> Seus Resultados<\/h3><div class=\"result-box\"><div class=\"field-result\" id=\"output-1\"><span class=\"field-title\"><span>Margem de erro<\/span><span class=\"result-term\">ME<\/span><\/span><span class=\"field-value\" id=\"result-1\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copiar resultado\" aria-label=\"Copiar resultado\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><div class=\"field-result\" id=\"output-2\"><span class=\"field-title\"><span>Limite de confian\u00e7a inferior<\/span><span class=\"result-term\">LCI<\/span><\/span><span class=\"field-value\" id=\"result-2\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copiar resultado\" aria-label=\"Copiar resultado\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><div class=\"field-result\" id=\"output-3\"><span class=\"field-title\"><span>Limite de confian\u00e7a superior<\/span><span class=\"result-term\">LCS<\/span><\/span><span class=\"field-value\" id=\"result-3\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copiar resultado\" aria-label=\"Copiar resultado\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><div class=\"field-result\" id=\"output-4\"><span class=\"field-title\"><span>Erro padr\u00e3o<\/span><span class=\"result-term\">EP<\/span><\/span><span class=\"field-value\" id=\"result-4\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copiar resultado\" aria-label=\"Copiar resultado\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><div class=\"field-result\" id=\"output-5\"><span class=\"field-title\"><span>Valor cr\u00edtico<\/span><span class=\"result-term\">z \/ t<\/span><\/span><span class=\"field-value\" id=\"result-5\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copiar resultado\" aria-label=\"Copiar resultado\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><div class=\"field-result is-column\" id=\"output-6\"><span class=\"field-title\"><span>Intervalo e detalhes<\/span><\/span><span class=\"field-value\" id=\"result-6\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copiar resultado\" aria-label=\"Copiar resultado\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><\/div><div class=\"result-actions\"><button type=\"button\" class=\"copy-link\"><svg viewBox=\"0 0 20 20\" fill=\"currentColor\" aria-hidden=\"true\"><path d=\"M12.232 4.232a2.5 2.5 0 0 1 3.536 3.536l-1.225 1.224a.75.75 0 0 0 1.061 1.06l1.224-1.224a4 4 0 0 0-5.656-5.656l-3 3a4 4 0 0 0 .225 5.865.75.75 0 0 0 .977-1.138 2.5 2.5 0 0 1-.142-3.667l3-3Z\"\/><path d=\"M11.603 7.963a.75.75 0 0 0-.977 1.138 2.5 2.5 0 0 1 .142 3.667l-3 3a2.5 2.5 0 0 1-3.536-3.536l1.225-1.224a.75.75 0 0 0-1.061-1.06l-1.224 1.224a4 4 0 1 0 5.656 5.656l3-3a4 4 0 0 0-.225-5.865Z\"\/><\/svg><span class=\"copy-link__text\">Copiar link para este c\u00e1lculo<\/span><\/button><span class=\"sr-only\" role=\"status\" id=\"copy-link-status\"><\/span><\/div><\/div><a href=\"#respond\" class=\"hidden transition-opacity duration-300 opacity-0 w-50 text-sm justify-center items-center gap-2 px-4 py-2 rounded bg-gray-200 text-gray-700 hover:bg-gray-300\" id=\"leave-comment\"><span class=\"icon icon-comments\" aria-hidden=\"true\"><\/span>Deixar um coment\u00e1rio<\/a><\/form><\/section><section id=\"calc-reactions\" class=\"not-prose hidden my-12 bg-gradient-to-r from-primary-50 to-gray-50 border border-indigo-100 rounded-xl px-6 py-4 shadow-sm\" data-post=\"222\" aria-live=\"polite\" aria-labelledby=\"calc-reactions-title\"><p id=\"calc-reactions-title\" class=\"text-sm text-gray-500 text-center mb-2\">O que voc\u00ea achou deste resultado?<\/p><div role=\"group\" aria-labelledby=\"calc-reactions-title\" class=\"grid grid-cols-3 sm:flex sm:flex-row sm:justify-around gap-4 sm:items-center sm:flex-wrap\"><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"like\"><span class=\"reaction-count\" data-reaction-count=\"like\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\ude00 <\/span><span class=\"reaction-description font-medium\">Curti <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"helpful\"><span class=\"reaction-count\" data-reaction-count=\"helpful\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\udca1 <\/span><span class=\"reaction-description font-medium\">\u00datil <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"confused\"><span class=\"reaction-count\" data-reaction-count=\"confused\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\ude15 <\/span><span class=\"reaction-description font-medium\">Confuso <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"disappointed\"><span class=\"reaction-count\" data-reaction-count=\"disappointed\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\ude1e <\/span><span class=\"reaction-description font-medium\">Decepcionado <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"inaccurate\"><span class=\"reaction-count\" data-reaction-count=\"inaccurate\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\u274c <\/span><span class=\"reaction-description font-medium\">Impreciso <\/span><\/button><\/div><div id=\"reaction-message\" class=\"hidden mt-8 rounded-md border border-primary-100 bg-white\/50 backdrop-blur-sm px-4 py-2 text-sm text-center shadow-sm\"><\/div><\/section><div class=\"calcdash-ad not-prose calcdash-ad--calc_result calcdash-ad--in-article\"><ins class=\"adsbygoogle\" style=\"display:block\" data-ad-client=\"ca-pub-1721569815777345\" data-ad-slot=\"6317458308\" data-ad-layout=\"in-article\" data-ad-format=\"fluid\"><\/ins><script>(adsbygoogle = window.adsbygoogle || []).push({});<\/script><\/div>\n<style id=\"wpcoderpro-inline-1\">.formula-box {\r\n\tborder-bottom: none !important;\r\n}<\/style><section class=\"formula-box\" aria-labelledby=\"formula-title\">\r\n\t<div id=\"formula-title\" class=\"not-prose font-display mb-4\"><span class=\"icon icon-formula\" aria-hidden=\"true\"><\/span><h2>F\u00f3rmula do intervalo de confian\u00e7a<\/h2><\/div>\r\n\t<figure class=\"not-prose formula\">\r\n\t\t<figcaption class=\"formula-title\">F\u00f3rmula<\/figcaption>\r\n\t\t<div class=\"text-base text-gray-800\" id=\"formula\">\n\\\\[ \\\\text{IC da m\u00e9dia:} \\\\quad \\\\bar{x} \\\\pm t_{\\\\alpha\/2,\\\\,n-1}\\\\cdot\\\\frac{s}{\\\\sqrt{n}} \\\\qquad \\\\text{IC da propor\u00e7\u00e3o:} \\\\quad \\\\hat{p} \\\\pm z_{\\\\alpha\/2}\\\\cdot\\\\sqrt{\\\\frac{\\\\hat{p}(1-\\\\hat{p})}{n}} \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Onde:<\/strong><\/p>\n<ul>\n<li>\\\\(\\\\bar{x}\\) \u2014 m\u00e9dia amostral (estimativa pontual da m\u00e9dia populacional)<\/li>\n<li>\\\\(\\\\hat{p}\\) \u2014 propor\u00e7\u00e3o amostral, inserida como decimal (ex.: 0,55 para 55%)<\/li>\n<li>\\\\(s\\) \u2014 desvio padr\u00e3o amostral<\/li>\n<li>\\\\(n\\) \u2014 tamanho da amostra (n\u00famero de observa\u00e7\u00f5es)<\/li>\n<li>\\\\(t_{\\\\alpha\/2,\\\\,n-1}\\) \u2014 valor cr\u00edtico da distribui\u00e7\u00e3o t de Student com \\\\(n-1\\) graus de liberdade (usado quando \\\\(s\\) estima um \\\\(\\\\sigma\\) desconhecido)<\/li>\n<li>\\\\(z_{\\\\alpha\/2}\\) \u2014 valor cr\u00edtico da distribui\u00e7\u00e3o normal padr\u00e3o<\/li>\n<li>\\\\(\\\\alpha = 1 - \\\\text{n\u00edvel de confian\u00e7a}\\) \u2014 n\u00edvel de signific\u00e2ncia<\/li>\n<\/ul>\n<p>A f\u00f3rmula constr\u00f3i o intervalo como a estimativa pontual mais ou menos a margem de erro, em que a margem de erro \u00e9 um valor cr\u00edtico multiplicado pelo erro padr\u00e3o \\\\(SE = s\/\\\\sqrt{n}\\) (m\u00e9dia) ou \\\\(SE = \\\\sqrt{\\\\hat{p}(1-\\\\hat{p})\/n}\\) (propor\u00e7\u00e3o).<\/p>\n<p>\r\n<\/section>\n<style id=\"wpcoderpro-inline-2\">.calculation-box {\r\n\tborder-bottom: none !important;\r\n}<\/style><section id=\"calculation\" class=\"calculation-box\" aria-labelledby=\"calculation-title\">\r\n\t<div id=\"calculation-title\" class=\"not-prose font-display\"><span class=\"icon icon-unordered-list\" aria-hidden=\"true\"><\/span><h2>Intervalo de confian\u00e7a &ndash; exemplo de c\u00e1lculo<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Exemplo:<\/strong> uma amostra de 25 medi\u00e7\u00f5es tem m\u00e9dia 100 e desvio padr\u00e3o 15. Encontre o intervalo de confian\u00e7a de 95% para a m\u00e9dia populacional. Como \\\\(n &lt; 30\\) e o desvio padr\u00e3o populacional \u00e9 desconhecido, usa-se a distribui\u00e7\u00e3o t com \\\\(n - 1 = 24\\) graus de liberdade.<\/p>\n<p>\\\\[ SE = \\\\frac{s}{\\\\sqrt{n}} = \\\\frac{15}{\\\\sqrt{25}} = 3 \\]<\/p>\n<p>\\\\[ t_{0.025,\\\\,24} \\\\approx 2.0639, \\\\quad ME = 2.0639 \\\\times 3 \\\\approx 6.1917 \\]<\/p>\n<p>\\\\[ \\\\text{IC} = 100 \\\\pm 6.1917 = (93.8083,\\\\; 106.1917) \\]<\/p>\n<p><strong>Resultado:<\/strong> o intervalo de confian\u00e7a de 95% \u00e9 aproximadamente (93,81, 106,19), com uma margem de erro de &plusmn;6,19. Voc\u00ea pode reproduzir isso com os valores padr\u00e3o da calculadora.<\/p>\n<p>\n\r\n<\/section>\n<h2>Como usar a calculadora de intervalo de confian\u00e7a<\/h2>\n<ol>\n<li>Escolha o <strong>Tipo de estimativa<\/strong>: &ldquo;M\u00e9dia amostral&rdquo; para m\u00e9dias de dados medidos, ou &ldquo;Propor\u00e7\u00e3o amostral&rdquo; para porcentagens ou contagens de sucessos.<\/li>\n<li>Insira a <strong>M\u00e9dia amostral (x&#772;)<\/strong>. Para uma propor\u00e7\u00e3o, digite o valor como um decimal entre 0 e 1, por exemplo 0,55 para 55%.<\/li>\n<li>Se voc\u00ea selecionou uma m\u00e9dia, insira o <strong>Desvio padr\u00e3o amostral (s)<\/strong>. Esse campo fica oculto para propor\u00e7\u00f5es.<\/li>\n<li>Insira o <strong>Tamanho da amostra (n)<\/strong> &mdash; um n\u00famero inteiro de pelo menos 2.<\/li>\n<li>Selecione o <strong>N\u00edvel de confian\u00e7a<\/strong>: 80%, 90%, 95%, 98%, 99% ou 99,9%. 95% \u00e9 a escolha mais comum.<\/li>\n<li>Escolha o <strong>M\u00e9todo do valor cr\u00edtico<\/strong>. O modo padr\u00e3o &ldquo;Autom\u00e1tico&rdquo; usa a t de Student quando \\\\(n &lt; 30\\) e o valor z da normal quando \\\\(n \\\\ge 30\\). Escolha &ldquo;z normal&rdquo; apenas quando o desvio padr\u00e3o populacional \\\\(\\\\sigma\\) \u00e9 conhecido.<\/li>\n<li>Leia os resultados: <strong>Margem de erro<\/strong>, <strong>Limite inferior de confian\u00e7a<\/strong>, <strong>Limite superior de confian\u00e7a<\/strong>, <strong>Erro padr\u00e3o<\/strong>, o <strong>Valor cr\u00edtico<\/strong> usado e um bloco de detalhes com o intervalo completo e a interpreta\u00e7\u00e3o.<\/li>\n<\/ol>\n<h2>O que significa um intervalo de confian\u00e7a<\/h2>\n<p>Um intervalo de confian\u00e7a \u00e9 uma faixa de valores plaus\u00edveis para um par\u00e2metro populacional desconhecido, como uma m\u00e9dia ou uma propor\u00e7\u00e3o, com base em uma \u00fanica amostra. A m\u00e9dia amostral ou a propor\u00e7\u00e3o amostral \u00e9 apenas uma estimativa pontual &mdash; \u00e9 improv\u00e1vel que acerte exatamente o valor verdadeiro. O intervalo envolve essa estimativa com uma margem de erro que reflete o quanto a estimativa poderia plausivelmente mudar se voc\u00ea extra\u00edsse uma amostra diferente.<\/p>\n<p>O n\u00edvel de confian\u00e7a descreve o comportamento de longo prazo do procedimento, n\u00e3o a probabilidade de um intervalo espec\u00edfico. Se voc\u00ea repetisse a amostragem muitas vezes e calculasse um intervalo a cada vez, cerca de 95% desses intervalos (no n\u00edvel de 95%) conteriam o verdadeiro valor populacional. Depois que um intervalo \u00e9 calculado, ele cont\u00e9m o par\u00e2metro ou n\u00e3o cont\u00e9m; a incerteza est\u00e1 no m\u00e9todo, n\u00e3o no par de n\u00fameros isolado.<\/p>\n<p>A largura do intervalo carrega a maior parte da informa\u00e7\u00e3o pr\u00e1tica. Um intervalo estreito significa que a estimativa \u00e9 precisa; um intervalo largo significa que os dados deixam uma d\u00favida consider\u00e1vel. A largura cresce com o desvio padr\u00e3o e com o valor cr\u00edtico (maior confian\u00e7a &rarr; intervalo mais largo) e diminui \u00e0 medida que o tamanho da amostra aumenta &mdash; quadruplicar \\\\(n\\) reduz a margem de erro aproximadamente \u00e0 metade, porque o \\\\(SE\\) \u00e9 dividido por \\\\(\\\\sqrt{n}\\).<\/p>\n<h2>Refer\u00eancia: valores cr\u00edticos comuns (bicaudais)<\/h2>\n<table>\n<thead>\n<tr>\n<th>N\u00edvel de confian\u00e7a<\/th>\n<th>Valor cr\u00edtico z<\/th>\n<th>t (gl = 24, para compara\u00e7\u00e3o)<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>80%<\/td>\n<td>1,2816<\/td>\n<td>1,3178<\/td>\n<\/tr>\n<tr>\n<td>90%<\/td>\n<td>1,6449<\/td>\n<td>1,7109<\/td>\n<\/tr>\n<tr>\n<td>95%<\/td>\n<td>1,9600<\/td>\n<td>2,0639<\/td>\n<\/tr>\n<tr>\n<td>98%<\/td>\n<td>2,3263<\/td>\n<td>2,4922<\/td>\n<\/tr>\n<tr>\n<td>99%<\/td>\n<td>2,5758<\/td>\n<td>2,7969<\/td>\n<\/tr>\n<tr>\n<td>99,9%<\/td>\n<td>3,2905<\/td>\n<td>3,7454<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>Pressupostos, limita\u00e7\u00f5es e dicas<\/h2>\n<ul>\n<li><strong>Amostragem aleat\u00f3ria.<\/strong> O intervalo s\u00f3 \u00e9 v\u00e1lido para a popula\u00e7\u00e3o efetivamente amostrada. Amostras n\u00e3o aleat\u00f3rias ou de conveni\u00eancia invalidam a garantia de cobertura.<\/li>\n<li><strong>t vs. z.<\/strong> Quando o desvio padr\u00e3o populacional \u00e9 desconhecido e estimado por \\\\(s\\), a t de Student \u00e9 a distribui\u00e7\u00e3o correta; ela leva em conta a incerteza extra ao estimar \\\\(\\\\sigma\\) e produz um intervalo mais largo e mais honesto, especialmente para \\\\(n\\) pequeno. Use z apenas quando \\\\(\\\\sigma\\) \u00e9 realmente conhecido ou quando \\\\(n\\) \u00e9 grande o suficiente para que a diferen\u00e7a seja desprez\u00edvel.<\/li>\n<li><strong>Normalidade.<\/strong> Para amostras pequenas, o intervalo baseado na m\u00e9dia pressup\u00f5e que os dados subjacentes sejam aproximadamente normais. Para \\\\(n \\\\ge 30\\), o teorema central do limite torna esse pressuposto em grande parte desnecess\u00e1rio, a menos que os dados sejam extremamente assim\u00e9tricos.<\/li>\n<li><strong>Propor\u00e7\u00f5es.<\/strong> O intervalo de Wald usado para propor\u00e7\u00f5es baseia-se em uma aproxima\u00e7\u00e3o normal. Funciona bem quando \\\\(n\\\\hat{p} \\\\ge 5\\) e \\\\(n(1-\\\\hat{p}) \\\\ge 5\\); a calculadora avisa quando essa condi\u00e7\u00e3o falha. Para amostras pequenas ou propor\u00e7\u00f5es pr\u00f3ximas de 0 ou 1, um intervalo de Wilson (score) \u00e9 mais confi\u00e1vel.<\/li>\n<li><strong>Maior confian\u00e7a custa largura.<\/strong> Passar de 95% para 99% alarga o intervalo visivelmente. Escolha o n\u00edvel adequado \u00e0 gravidade de um erro na sua aplica\u00e7\u00e3o, e n\u00e3o simplesmente o n\u00famero mais impressionante.<\/li>\n<li><strong>N\u00e3o confunda precis\u00e3o com confian\u00e7a.<\/strong> Um intervalo de 99% obtido com 10 observa\u00e7\u00f5es pode ser t\u00e3o largo que se torna praticamente in\u00fatil. Aumentar \\\\(n\\), e n\u00e3o o n\u00edvel de confian\u00e7a, \u00e9 o caminho para obter um intervalo estreito.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Calcule um intervalo de confian\u00e7a para uma m\u00e9dia ou propor\u00e7\u00e3o populacional. Insira as estat\u00edsticas da sua amostra, escolha um n\u00edvel de confian\u00e7a e obtenha a margem de erro e os limites inferior e superior.<\/p>\n","protected":false},"author":3168,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[12],"tags":[68],"class_list":["post-222","post","type-post","status-publish","format-standard","hentry","category-estatistica","tag-tamanho-da-amostra"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/posts\/222","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/users\/3168"}],"replies":[{"embeddable":true,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/comments?post=222"}],"version-history":[{"count":1,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/posts\/222\/revisions"}],"predecessor-version":[{"id":2339,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/posts\/222\/revisions\/2339"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/media?parent=222"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/categories?post=222"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/pt\/wp-json\/wp\/v2\/tags?post=222"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}