What are the basic requirements of valid experiments?
Four basic components that affect the validity of an experiment are the control, independent and dependent variables, and constants. These basic requirements need to be present and identified to consider an experiment valid.
What are internal and external threats to validity?
External validity is the extent to which your results can be generalized to other contexts. There are eight threats to internal validity: history, maturation, instrumentation, testing, selection bias, regression to the mean, social interaction and attrition.
What are some threats to external validity?
There are seven threats to external validity: selection bias, history, experimenter effect, Hawthorne effect, testing effect, aptitude-treatment and situation effect.
What is sample size bias?
In statistics, sampling bias is a bias in which a sample is collected in such a way that some members of the intended population have a lower or higher sampling probability than others. Ascertainment bias has basically the same definition, but is still sometimes classified as a separate type of bias.
What makes a sample representative of a population?
A representative sample is a subset of a population that seeks to accurately reflect the characteristics of the larger group. For example, a classroom of 30 students with 15 males and 15 females could generate a representative sample that might include six students: three males and three females.
Why is it important to use a random sample?
Random sampling ensures that results obtained from your sample should approximate what would have been obtained if the entire population had been measured (Shadish et al., 2002). The simplest random sample allows all the units in the population to have an equal chance of being selected.
Can random sampling be biased?
Although simple random sampling is intended to be an unbiased approach to surveying, sample selection bias can occur. When a sample set of the larger population is not inclusive enough, representation of the full population is skewed and requires additional sampling techniques.