Some examples for Stat 3022, Mar 26, 2007
R: x <- c(42, 38, 11, 9) names(x) <- c("Fort", "C", "Pasc", "Java") p0 <- c(0.4, 0.25, 0.25, 0.1) chisq.test(x, p = p0) ##### by hand ##### n <- sum(x) k <- length(x) e <- n * p0 names(e) <- names(x) e Xsq <- sum((x - e)^2 / e) Xsq 1 - pchisq(Xsq, k - 1)
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R: x <- matrix(c(126, 44, 51, 149, 41, 26), nrow = 3) dimnames(x) <- list(c("very effective", "somewhat effective", "not effective"), c("preteen", "teen")) x chisq.test(x) ##### by hand ##### n <- sum(x) k1 <- nrow(x) k2 <- ncol(x) p1 <- apply(x, 1, sum) / n p2 <- apply(x, 2, sum) / n p1 p2 e <- n * outer(p1, p2) dimnames(e) <- dimnames(x) e Xsq <- sum((x - e)^2 / e) Xsq 1 - pchisq(Xsq, (k1 - 1) * (k2 - 1))