###################################################################### # Grading with a bell curve # # # ###################################################################### ##################################################################### # Example #1 curve(expr = dnorm(x = x, mean = 73, sd = 8), n = 1000, from = 50, to = 100, col = "darkgreen", lwd = 2, ylab = "f(y)", xlab = "y") abline(h = 0) segments(x0 = 90, y0 = 0, x1 = 90, y1 = dnorm(x = 90, mean = 73, sd = 8), col = "red", lwd = 5) 1 - pnorm(q = 90, mean = 73, sd = 8) ##################################################################### # Example #2 curve(expr = dnorm(x = x, mean = 73, sd = 8), n = 1000, from = 50, to = 100, col = "darkgreen", lwd = 2, ylab = "f(y)", xlab = "y") abline(h = 0) segments(x0 = 90, y0 = 0, x1 = 90, y1 = dnorm(x = 90, mean = 73, sd = 8), col = "red", lwd = 5) segments(x0 = 70, y0 = 0, x1 = 70, y1 = dnorm(x = 70, mean = 73, sd = 8), col = "red", lwd = 5) pnorm(q = 90, mean = 73, sd = 8) - pnorm(q = 70, mean = 73, sd = 8) ##################################################################### # Example #3 curve(expr = dnorm(x = x, mean = 73, sd = 8), n = 1000, from = 50, to = 100, col = "darkgreen", lwd = 2, ylab = "f(y)", xlab = "y", ylim = c(0,0.14)) curve(expr = dnorm(x = x, mean = 62, sd = 3), n = 1000, from = 50, to = 100, col = "blue", lwd = 2, ylab = "f(y)", xlab = "y", add = TRUE) abline(h = 0) legend(x = 70, y = 0.12, legend = c("mu = 73, sigma = 8", "mu = 62, sigma = 3"), lty = c(1,1), col = c("darkgreen", "blue"), bty = "n", lwd = c(2,2)) qnorm(p = 0.90, mean = 73, sd = 8) qnorm(p = 0.90, mean = 62, sd = 3) #