Random Variance

A Random Variance is a variance metric that is due to random effects not expected by experiment.

• AKA: Unsystematic Variance, Unexplained Variance.
• Context:
  • It can be measured as a standard error or sum of squares.
• Example(s):
  • Variance within Groups.
• Counter-Example(s):
  • Systematic Variance.
  • Difference between Means Variance.
  • Variance between Groups.
• See: Test Statistic, Population Sample, F-statistic, t-statistic Comparison of Means Test.

---

---

References

2016

• (Changing Minds, 2016) ⇒ http://changingminds.org/explanations/research/analysis/test_statistic.htm
  • QUOTE: Unsystematic variance is that which is unintended and is a particularly tricky problem in social research. People are not like physical objects. The same person might answer the same question differently on different days. They might understand a lesson differently depending on what other stressors there are in their lives. It is because of this that we do social experiments and pay a lot of attention to systematic vs unsystematic variance. It would otherwise be too easy to draw conclusions based more on coincidence than reliable fact. Unsystematic variance is generally measured as the variation within groups, across a group of subjects where you might hope that a similar set of scores are found. This is typically calculated as the sum of the squares, SS, standard error, or another measure of spread. Unsystematic variance is often denoted as SSR, where 'R' stands for 'residual' (ie that which is left over when the systematic variance is removed from the total variance. An easy way of remembering this is that it is also due to Random effects.

---