Attaching unwarranted significance to aspects of the numbers that do not convey meaningful information
Failing to simply data when would easily do so
Manipulating our data in ways that destroy information
Performing meaningless statistical operations on the data
Nominal and ordinal measurement
Nominal measurement: not measurement in the everyday sense of the word; the value does not imply any ordering of the cases, for example, shirt numbers in football; Even though player 17 has higher number than player 7, you can’t say from the data that he’s greater than or more than the other.
When attributes can be rank-ordered
Distances between attributes do not have any meaning, for example, the distance between the winner of a sport competition and the second one, and between the second and third one
The Hierarchy of Levels
Attributes are only named; weakest
Attributes can be ordered
Distance is meaningful
Types of data
Nominal and ordinal are qualitative (categorical) levels of measurement.
Interval and ratio are quantitative levels of measurement.
Example: Identify each of the following as examples of (1) nominal, (2) ordinal, (3) discrete, or (4) continuous variables:
1. The length of time until a pain reliever begins to work.
2. The number of chocolate chips in a cookie.
3. The number of colors used in a statistics textbook.
4. The brand of refrigerator in a home.
5. The overall satisfaction rating of a new car.
6. The number of files on a computer’s hard disk.
7. The pH level of the water in a swimming pool.
8. The number of staples in a stapler.
Measure and Variability
No matter what the response variable: there will always be variability in the data.
One of the primary objectives of statistics: measuring and characterizing variability.
Controlling (or reducing) variability in a manufacturing process: statistical process control.
Methods used to collect data
Census: A 100% survey. Every element of the population is listed. Seldom used: difficult and time-consuming to compile, and expensive.
Survey: Data are obtained by sampling some of the population of interest. The investigator does not modify the environment.
Experiment: The investigator controls or modifies the environment and observes the effect on the variable under study.
Administrative resources: The source of the data is an administrative activity.