For each of the following problems, which measure of central tendency should be computed?

(a) An experimental psychologist wants a measure of central tendency for the number of trials taken to learn a task by 45 eight-year-old children. The maximum number of trials allowed is 30. Most of the children took between 14 trials and 30 trials to learn the task, but five children did not learn the task at all even after 30 trials.

(b) A student who has taken 25 college courses, each of which is worth 3 credits, wants to compute her grade point average.

(c) A student who has taken 25 college courses, some of which are worth 3  redits and some 4 credits, wants to compute his grade point average.

(d) A researcher wants a measure of central tendency for the income of a sample of 100 people that includes Bill Gates and Tiger Woods. (e) The editor of a college student yearbook wants to decide the color of the cover and asks the 30 students working on the yearbook to vote for orange, blue, green, or black.