posted by Kathryn on .
If a large number of people guess randomly on each of 100 items on a true-false test, the mean would be expected to be ì=___*, and ó=__*.
What % of the examinees would be expected to get a score of 65 or >?
The mean is p*N = 50
where p is the probability of getting gthe correct answqer by guessing at random. N is the number of tosses
The variance is p(1 -p)N = 25
The standard deviation is
ó = sqrt25 = 5.
Use a normal ditributuion curve for the probability of getting a score of 65 or better. You are talking 3 sigma from the mean.