Question

The SAT is a multiple-choice test. Each question has five possible answers. The test taker must select one answer for each question or not answer the question. One point is awarded for each correct response, and 1/4 point is subtracted for each wrong answer. No points are added or subtracted for answers left blank. Find the expected point value of a random guess.

Answer 1

what is the prob. of a right guess?

Answer 2

1/5

Answer 3

and that of a wrong one?

Answer 4

4/5

Answer 5

now expectation is sum of prob x value

Answer 6

sorry im confused

Answer 7

see
expectation is Value of Something x Probability of that somthing

Answer 8

so the value would be 1 for one guess? x 1/5 or 4/5?

Answer 9

its like
Value of right guess x prob of right guess
+
Value of wrong guess x prob of wrong guess

Answer 10

okay so 1 x 1/5 + (-1/4) x 4/5

Answer 11

that would be 0

Answer 12

just visualize the prob...u will get 5 chances....1 right = 1 point
4 wrong = - 1 point
so if u just guess you will get nothing

Answer 13

thanks!

Answer 14

me?

Answer 15

both

Answer 16

thanks!

Answer 17

haha ikr...i was messing