Astronomers use statistics because they can't manipulate the universe in a laboratory the way a chemist can manipulate a compound or a biologist can manipulate a specimen. Since it is impossible to perturb some part of the population in order to see its effect, astronomers rely on standard sampling design and estimation methods in order to make conclusions regarding the universe.
Also, processes in the universe take place over a very large time scale so noticeable changes are rare and tend to be studied in detail. As an example, consider stellar evolution. No one has ever observed a star go through its life cycle since the shortest cycles are about 10 million years long, but astronomers can observe many stars at different stages in their life cycles and make predictions.
Astronomers use two different sampling designs depending on the population being studied. If the population is finite in size, such as a cluster of stars or the Hubble Deep Fields, simple random sampling is chosen. If the population is very large and considered infinite, then more complex designs are used depending on the characteristics of the population and the property being studied. Active galactic nuclei and halo stars are two populations that are considered infinite.
"Q&A: Statistics and astronomy" is a series of questions and answers about statistics written for teachers and students. The questions are ones that students might ask while studying statistics. Teachers can use this Q&A to gain additional knowledge about statistics, or use it in the classroom as outlined below.
• An engagement activity. Use selected questions to start a discussion.
• An inquiry tool. Use selected questions and answers to help students generate questions. Propose a question, such as "Why do astronomers use statistics? Have students read the answer to the question and write down 3–5 questions they would like answered as a result of reading the material.
• A source of information. Students can use the questions and answers as part of their research on statistics.
• A form of review. Use the questions as a review at the end of a unit on statistics.
• A follow-up. Have students read the questions and answers to gain additional information about statistics following a related activity.
• A starting point for debate. "If statistics are flawed with error, why do astronomers rely on them?" This idea is addressed in the question "Why do astronomers use statistics?"
Online Exploration: Galaxy Hunter