The question types on an IQ exam include mathematical and verbal analogies, logic problems, and problems in mathematical pattern completion. An example of a verbal analogy problem asks the test-taker to select the word that best completes the comparison, "Book is to reading as fork is to"; the correct answer is the multiple choice option "eating."
Formal IQ tests, which are usually performed by psychologists, are meant to test many different types of intelligence. Test-takers may see questions that require them to find the next number in a sequence of numbers by determining a pattern, such as consecutive numbers decreasing or increasing by a specific amount. They might also see questions that require them to group sets of words based on similar meaning or to determine which 3-D shape can be formed by presenting an unfolded representation of that shape.
In grade school and high school level tests, IQ test results can be influenced by many factors including how much schooling the test-taker has received and how nutritious his diet is. The results of the IQ test can be used to predict financial success, with those who score higher tending to earn more money in their lifetime. Over time the IQ of the general population has been increasing, as of 2015.