{"id":294,"date":"2014-10-05T22:10:57","date_gmt":"2014-10-05T20:10:57","guid":{"rendered":"http:\/\/wordpress.callac.online\/index.php\/risque-relatif-et-odds-ratio-avec-r\/"},"modified":"2023-10-14T20:14:41","modified_gmt":"2023-10-14T18:14:41","slug":"risque-relatif-et-odds-ratio-avec-r","status":"publish","type":"page","link":"https:\/\/wordpress.callac.online\/index.php\/logiciels-mathematiques\/le-logiciel-r\/les-tests-avec-r\/risque-relatif-et-odds-ratio-avec-r\/","title":{"rendered":"Risque relatif et odds-ratio avec R"},"content":{"rendered":"

<\/h2>\n

Un fichier de donn\u00e9es<\/h2>\n

Travaillons sur une enqu\u00eate de satisfactions dans un h\u00f4pital, r\u00e9cup\u00e9r\u00e9 lors d’un cours de FUN (France Unit\u00e9 Num\u00e9rique). Les fichiers sont disponibles ici<\/a>.<\/p>\n

Par la suite, ces donn\u00e9es seront stock\u00e9es dans la variable satis<\/em> .<\/p>\n

Dans ces donn\u00e9es comme souvent, les observations sont en lignes et les variables en colonnes.<\/p>\n

Pr\u00e9sentation<\/h2>\n\n\n\n\n\n
<\/td>\n$M$<\/td>\n$\\overlineM<\/em>$<\/td>\n<\/tr>\n
$FR$<\/td>\n$a$<\/td>\n$b$<\/td>\n<\/tr>\n
$\\overlineFR<\/em>$<\/td>\n$c$<\/td>\n$d$<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Dans le tableau d’effectifs pr\u00e9c\u00e9dent, $M$ sont les malades et $FR$ ceux qui pr\u00e9sentent un facteur de risque.<\/p>\n

On a alors les d\u00e9finitions suivantes :<\/p>\n

– Risque relatif : RR=\\frac{\\frac{a}{a+b}}{\\frac{c}{c+d}} <\/span><\/p>\n

– Odds-ratio : \u00a0 OR=\\frac{\\frac{a}{b}}{\\frac{c}{d}} <\/span><\/p>\n

Le risque relatif est \u00e0 utiliser lorsqu’on a les statistiques d’une population g\u00e9n\u00e9rale.
\nL’odds-ration est plus robuste sur un \u00e9chantillon, et notamment en cas d’enqu\u00eate cas-t\u00e9moins.<\/p>\n

Un cas concret<\/h2>\n

Etudions si le fait de recommander l’h\u00f4pital est li\u00e9 au fait d’avoir la profession 2.<\/p>\n

Pour cela, pr\u00e9parons les donn\u00e9es binaires utiles.<\/p>\n

satis$recommander.b<-ifelse(satis$recommander==2,1,0) \nsatis$prof2.b<-ifelse(satis$profession==2,1,0)<\/pre>\n
Donnons le tableau associ\u00e9 :<\/p>\n
table(satis$prof2.b,satis$recommander.b,deparse.level=2)<\/pre>\n

\nsatis$recommander.b
\nsatis$prof2.b   0   1
\n0 124 239
\n1   9  28
\n<\/code><\/p>\n
Comme la maladie et le facteur de risque sont normalement cod\u00e9 en 0 au lieu de 1, vaut mieux inverser le tableau :<\/p>\n
table(1-satis$prof2.b,1-satis$recommander.b,deparse.level=2)<\/pre>\n

\n1 - satis$recommander.b
\n1 - satis$prof2.b   0   1
\n0  28   9
\n1 239 124
\n<\/code><\/p>\n
Pour r\u00e9aliser le test, on utilise la commande twoby2(FR,Maladie)<\/em>. On respectera cet ordre pour que le risque relatif calcul\u00e9 soit le bon.<\/p>\n
library(Epi)\ntwoby2(1-satis$prof2.b,1-satis$recommander.b)<\/pre>\n

\n2 by 2 table analysis: <\/code><\/p>\n
<\/code><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/p>\n
\n
<\/code><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/p>\n
Outcome : 0
\nComparing : 0 vs. 1<\/p>\n
<\/code><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/p>\n
0 1 P(0) 95% conf. interval
\n0 28 9 0.7568 0.5948 0.8683
\n1 239 124 0.6584 0.6081 0.7054<\/p>\n
<\/code><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/p>\n
95% conf. interval
\nRelative Risk: 1.1494 0.9437 1.3998
\nSample Odds Ratio: 1.6141 0.7387 3.5272
\nConditional MLE Odds Ratio: 1.6123 0.7120 4.0092
\nProbability difference: 0.0984 -0.0664 0.2189<\/p>\n
<\/code><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/p>\n
Exact P-value: 0.2737
\nAsymptotic P-value: 0.23<\/p>\n
<\/code><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/p>\n
\n

\n<\/code><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/p>\n
<\/code><\/p>\n
On constate que $OR$ <\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em>est \u00e9lev\u00e9 mais la valeur de $p$ <\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em>sup\u00e9rieure \u00e0 $5~\\%$ <\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em><\/em>ne permet pas de conclure.<\/p>\n","protected":false},"excerpt":{"rendered":"
Un fichier de donn\u00e9es Travaillons sur une enqu\u00eate de satisfactions dans un h\u00f4pital, r\u00e9cup\u00e9r\u00e9 lors d’un cours de FUN (France Unit\u00e9 Num\u00e9rique). Les fichiers sont disponibles ici. Par la suite,…<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":2089,"menu_order":4,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-294","page","type-page","status-publish","hentry"],"yoast_head":"\nRisque relatif et odds-ratio avec R - Maths & Num\u00e9rique<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/wordpress.callac.online\/index.php\/logiciels-mathematiques\/le-logiciel-r\/les-tests-avec-r\/risque-relatif-et-odds-ratio-avec-r\/\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Risque relatif et odds-ratio avec R - Maths & Num\u00e9rique\" \/>\n<meta property=\"og:description\" content=\"Un fichier de donn\u00e9es Travaillons sur une enqu\u00eate de satisfactions dans un h\u00f4pital, r\u00e9cup\u00e9r\u00e9 lors d’un cours de FUN (France Unit\u00e9 Num\u00e9rique). 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