Is a multiple choice test of intelligence too easy if the mean correct is close to the number of items? I have a mean score of 28 out of 30  and a sd of 12 for a multiple choice test of intelligence , does this mean the test is too easy?
 A: If you are trying to measure individual differences and the mean on the test is 28 items correct out of 30, then yes, the test is too easy for your sample. A large proportion of the sample is not being reliably differentiated.
Greater reliability would typically be achieved where the mean is closer to the mid-point between zero and number of items (perhaps with an increment for proportion guessing items correct - see here.
The standard deviation is presumably large, because you have a small percentage of the sample who got very few correct and the majority of the sample who got  everything or almost everything correct. To verify this, check out a frequency table or histogram.
Such a distribution of scores is reasonable for certain multiple choice tests. For example, if you were trying to assess competence, as if often the case for training modules in the workplace, it is reasonable for most people to perform above cut-off. Then it's really about determining whether people truly are competent if they achieve above cut-off.
A: The high mean would lead me to believe that yes, your test is too easy.  However, considering such a large sd, I would say no, your test is not too easy. 
The high sd means there was a large spread in your test scores, differentiating high and low intelligence test takers.  However, you need scores that fall multiple sd's above and below your mean to differentiate between 1sd smart people and 2 sd smart people.  Your test does not do that.
Ideally you would want a mean of 20 out of 30, with a sd below 5.  This would help you differentiate your test takers better.  How you do that is another story.
