IQ tests usually measure specific knowledge, vocabulary, expressive language and memory skills, visual-spatial abilities, fine motor coordination, and perceptual skills. Many of them depend on speed for scoring. IQ tests measure, for the most part, what a person has learned, not the persons capability or potential.A high IQ score does not guarantee success in later life, nor does it guarantee success in school. People with very high IQs have been known to work in menial jobs. Some people who did poorly in school often turn out to be very successful in later life. A person may have failed dismally in school, and yet turn out to be a successful businessman.

And many highly successful people have been shown to have average IQ scores.

IQ tests only measure a certain potential which still needs to be developed and nurtured by its owner. If the person does not have the inclination or desire to do so, then that potential remains underutilized or even unutilised.

IQ tests predict who has a certain type of intellectual potential, but they don’t necessarily predict who will become a good businessman, successful doctor, a popular leader, a great scientist, or a good parent. Success in life is determined by qualities such as determination, vision, creativity, optimism,  flexibility, common sense, social skills, the ability to get along with other people, to be optimistic, to be determined, and knowing a good idea when you see one. None of these are assessed by IQ tests. The only thing IQ tests can really predict is who will do well on IQ tests.

If you have had your IQ tested and you have got a score in the average range it does not in any way mean you are limited to a life of average success and average accomplishment.If your IQ is in the above average range, it does not guarantee you a successful  life and career.

Your IQ score is only a number. It does not define you. It does not really limit you. It’s just a starting point. Remember that many other qualities you already possess or can develop are also important for success in life.

While some of the standardized IQ tests such as the Wechsler Adult Intelligence Scale, Wechsler Intelligence Scale for Children, Stanford-Binet, Woodcock-Johnson III Tests of Cognitive Abilities, or the Kaufman Assessment Battery for Children-II, also test factors that  represent measures of intelligence. the same cannot be said of the hundreds of online tests marketing themselves as IQ Tests.  

Intelligence can be defined as a person's capacity to (1) acquire knowledge (i.e. learn and understand), (2) apply knowledge (solve problems), and (3) engage in abstract reasoning. While IQ scores do have high predictive validity for individual differences in school achievement, they have little ability to predict individual success or career progression.

IQ tests were originally used to detect children of lower intelligence, in order to place them in special education programs. Tests of IQ tests are designed to compare a child's intelligence to what his or her intelligence "should be" as compared to the child's age. If the child was significantly "smarter" than a "normal" child of his or her age, the child was given a higher score, and if the child scored lower than expected for a child of his or her age, the child was given a lower IQ score.

The only clinical use of IQ tests today is to detect mild mental retardation. Mental Retardation (MR) is characterized by significantly impaired cognitive functioning and has historically been defined as an IQscore less than 70.

In early childhood mild mental retardation (IQ 50–69) may not be identified until the child begins school. It may take expert assessment to distinguish mild mental retardation from conditions such as Learning Disability or emotional and / or behavioral disorders. As individuals with mild mental retardation reach adulthood, many learn to live independently and maintain gainful employment.