```{r data generation, echo = FALSE, results = "hide"} ## success probability in percent (= pay with card) p <- sample(15:30, size = 1) ## number of attempts (= customers in queue) n <- sample(6:9, size = 1) ## minimum number of successes (= customers who pay with card) k <- sample(1:3, 1) ## compute the correct solution in percent sol <- 100 * pbinom(k - 1, size = n, prob = p/100, lower.tail = FALSE) ok <- FALSE while(!ok) { ## two typical errors: 1-p vs. p, pbinom vs. dbinom err1 <- 100 * pbinom(k - 1, size = n, prob = 1 - p/100, lower.tail = FALSE) err2 <- 100 * dbinom(k, size = n, prob = p/100) ## two random errors rand <- runif(2, min = 0, max = 100) ## make sure solutions and errors are unique ans <- round(c(sol, err1, err2, rand), digits = 2) ok <- length(unique(ans)) == 5 } ``` Question ======== According to a recent survey `r 100 - p` percent of all customers in grocery stores pay cash while the rest use their credit or cash card. You are currently waiting in the queue at the checkout of a grocery story with `r n` customers in front of you. What is the probability (in percent) that `r k` or more of the other customers pay with their card? ```{r questionlist, echo = FALSE, results = "asis"} answerlist(ans, markup = "markdown") ``` Meta-information ================ extype: schoice exsolution: 10000 exname: binomial v3 exshuffle: TRUE