Key Terms

Autism spectrum disorder

Autism spectrum disorder (ASD) is a developmental disability that is caused by differences in how the brain functions. People with ASD may communicate, interact, behave, and learn in different ways. Signs of ASD begin during early childhood and usually last throughout a person’s life (1). ASD includes former diagnoses of autistic disorder, pervasive developmental disorder, not otherwise specified (PDD-NOS), and Asperger disorder. These diagnoses were collapsed into the single category of ASD in 2013.

Confidence interval

A confidence interval gives an estimated range of values which is likely to include the information (e.g., prevalence) that we want to know about.  The interval is a range of values that you can have confidence contains the true value in the population. There are different levels of confidence intervals; the most common is 95%. With a 95% confidence interval, we say that we are 95% confident that the value in our population will be included in our interval.  5% of the time, it will not.  So, we could say, “We are 95% confident that the prevalence of ASD in 8-year-olds in our surveillance area was between 21 and 27 per 1,000 children in 2014. Larger samples typically have smaller confidence intervals.  Smaller samples usually have bigger confidence intervals.

Developmental delay

A developmental delay is a persistent delay experienced by a child in reaching one or more developmental milestones—how children grow, move, communicate, interact, learn, and play.

Intellectual disability

Intellectual disability means that a person has difficulty learning at an expected level and functioning in daily life. In this report, intellectual disability is measured by intellectual quotient (IQ) test scores of less than or equal to 70.

IQ Test

A standardized psychological test or tool used to measure an individual's overall “intelligence quotient” (IQ). These tests often measureproblem-solvingg skills across a variety of domains.


Prevalence is a scientific term that describes the number of people with a disease or condition among a defined group at a specific period in time. Prevalence is usually expressed as a percentage or proportion of the defined group. For this project, we counted the number of 8-year-olds in 2014 who were identified with ASD and then divided that number by the total number of 8-year-olds in our surveillance area during 2014.

Statistical significance

The likelihood that a relationship between two or more variables is caused by something besides random chance.