Last Modified: 2014-08-18
- The difference between values can be measured.
- The difference between a temperature of 100 degrees and 90 degrees is the same difference as between 90 degrees and 80 degrees.
- A ratio variable, has all the properties of an interval variable, and also has a clear definition of 0.0
- Zero equals nothing or none
corresponding measurements from the respective population.
- Groups or classes inside a population that share a common characteristic are called strata.
- In the population of all undergraduate college students, some strata might be freshmen, sophomores, juniors, or seniors.
- Involves first selecting a fixed starting point in the larger population, and then
- Obtaining subsequent observations by using a constant interval between samples taken
- When "natural" groupings are evident in a statistical population
- The total population is divided into these groups (or clusters) a sample of the groups is selected
- Often used in marketing research
affect the treatment.
- Individuals are first sorted into blocks, and
- Then a random process is used to assign each individual in the block to one of the treatments.
- Used to assign individuals to the two treatment groups.
- This helps prevent bias in selecting members for each group.
- The question may be worded in such a way as to elicit a specific response.
- The order of questions might lead to biased responses.
- Likert scale forces responses that don't reflect respondent's feelings.
- Individuals with strong feelings about a subject are more likely than others to respond.
- Such a study is interesting but not reflective of the population.
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