Question | Answer |
Data | consist of information coming from observations, counts, measurements, or responses. |
Statistics | the science of collecting, organizing, analyzing, and interpreting data in order to make decisions. |
Population | the collection of all outcomes, responses, measurements, or counts that are of interest. |
Sample | a subset of a population. |
Parameter | a numerical description of a population characteristic. |
Statistic | a numerical description of a sample characteristic. |
Descriptive statistics | the branch of statistics that involves the organization, summarization, and display of data. |
Inferential statistics | the branch of statistics that involves using a sample to draw conclusions about a population. A basic tool in the study of inferential statistics is probability. |
Qualitative data | consist of attributes, labels, or nonnumerical entries. |
Quantitative data | consist of numerical measurements or counts. |
Nominal level of measurement | qualitative only. Data at this level are categorized using names, labels, or qualities. No mathematical computations can be made at this level. |
Ordinal level of measurement | qualitative or quantitative data. Data at this level can be arranged in order, or ranked, but differences between data entries are not meaningful. |
Interval level of measurement | data that can be ordered, and you can calculate meaningful differences data entries. At this level, a zero entry simply represents a position on a scale; the entry is not an inherent zero. |
Ratio level of measurement | data that are similar to data at the interval level, with the added property that a zero entry is an inherent zero. A ratio of two data values can be formed so that one data value can be meaningfully expressed as a multiple of another. |
Observational study | a method of gathering data in which a researcher observes and measures the characteristics of interest of part of a population but does not change existing conditions. |
Experiment | a method of gathering data in which a researcher applies a treatment to part of the population and then observes and measures the responses of interest of part of a population. |
Control group | the part of the population to which no treatment is applied in an experiment. |
Experimental units | the subjects involved in an experiment. |
Placebo | a harmless, unmediated treatment given to subjects in an experiment; it is made to look like the real treatment. |
Simulation | a method of gathering data that uses a mathematical or physical model to reproduce the conditions of a impractical, expensive, or dangerous situation or process. |
Survey | a method of gathering data which is an investigation carried out by asking people questions by interview, mail, or telephone. |
Confounding variable | occurs when an experimenter cannot tell the difference between the effects of different factors on a variable. |
Placebo effect | occurs when a subject reacts favorably to a placebo when in fact he or she has been given no medicate treatment at all. |
Blinding | a technique where the subject does not know whether he or she is receiving a treatment or placebo. |