getRandSamples <- function(seed = NA){
  if (!is.na(seed)){
    set.seed(seed) #incase you need repeatable data generation.
    #but remember to set a different seed for each person if you want them to get different items at each time point.
  }

  True_New <- sample(1:20,20,replace = F) #items that are true + new
  True_Rep <- sample(21:40,20,replace = F) #items that are true + repeated
  False_New <- sample(41:60,20,replace = F) #items that are false + new
  False_Rep <-sample(61:80,20,replace = F) # items that are false + repeated

  items <- list(True_New, True_Rep, False_New, False_Rep)

  t1 <- sapply(items, function(x) x[1:5]) #items to give at time 1
  t2 <- sapply(items, function(x) x[6:10]) #items to give at time 2
  t3 <- sapply(items, function(x) x[11:15]) #items to give at time 3
  t4 <- sapply(items, function(x) x[16:20]) #items to give at time 4

  #return dataframe with time and items for each time point
  return(data.frame(time = sort(rep(0:3,20)),
                    item = c(t1,t2,t3,t4)))
}