Assessment, Statistics, and Research

  The concept of average intelligence is sometimes difficult to appreciate because the two words, average and intelligence, are sometimes not defined. Average   To psychologists and counselors who administer tests of intelligence, a person who scores at the 50th Percentile has average intelligence as defined by the number of correct answers to test tasks compared to others in their age group. Many tests set the middle score at 100 thus, 100 = average intelligence on many tests. All test scores vary from time to time so, a person may earn more or less points on another day. This fluctuation is estimated and can range for example by plus or minus 3-5 IQ points depending on the test and age group.  If you retake the test in a month or so, you may score better because of the “practice effect”—you’ve seen the items recently so you will probably do better. There is an average range so examiners will not focus on the obtained score but consider a broader range. For example, some may consider