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Definition
| is a science that involves gathering information from numerical data obtained during an experiment or from a sample. It involves designing an experiment or sampling procedure, collecting the data, analyzing the data, and making inferences |
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| The entire group of subjects or individuals about which the researcher wants information |
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| Some characteristic of the population that the researcher wants to measure. |
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| A subset of the population that is contacted and examined to gather information. |
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| A descriptive measure, computed from data in a sample, that can be expressed or evaluated numerically |
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| A statement about a population based on the data collected in a sample. |
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| A listing of all the possible values that a characteristic can take and the number (or percentage) of times that each value occurs |
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| Branch of statistics concerned with numerical and graphical techniques for describing one or more characteristics of a population and for comparing characteristics among populations |
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| Branch of statistics in which we use information from a sample to make inferences (statements) about a population. |
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| A characteristic whose value does not change throughout the population of interest. |
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| A characteristic whose measurements vary (or change) from trial to trial or individual to individual. |
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| Qualitative or Categorical Variable |
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Definition
| A variable whose measurements vary in kind or name, but not in degree. This implies that one level of a categorical variable cannot be considered to be greater than or better than another level. |
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| A variable whose measurements vary in magnitude from trial to trial, meaning some order or ranking can be applied to the levels. |
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| Discrete Quantitative Variable |
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Definition
A quantitative variable whose measurements can assume only a countable number of possible values.
Examples: 1. Number of students in a particular class
2. Number of cars in a parking deck
3. Grades on a test |
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| Continuous Quantitative Variable |
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Definition
A quantitative variable whose measurements can assume any one of a countless number of values in a line interval. It is usually a measurable quantity or something that is calculated, such as rates, averages, proportions, and percentages.
Examples: 1. Weight of a typical student
2. Percentage of students who pass a
course |
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| exists when some subjects or individuals are systematically favored over others. |
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| occurs when one or more types of subjects are systematically excluded from the sample. |
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| When selection bias exists, the results from the sample can only be inferred to part of the population. The inference cannot be made to the entire population, but only a subset of the population. |
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Definition
| When an individual randomly chosen to be a part of the sample cannot be contacted or fails (or refuses) to respond |
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| When respondents give inaccurate information or if the interviewer influences the subject to respond in a certain way due to the way the questions are phrased |
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Definition
involves selecting a sample by some convenient mechanism that does not involve randomization.
Ex: a mall survey |
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| volunteer response sample |
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Definition
| subjects volunteer to be part of the study. Examples include telephone call-in polls, internet surveys, newspaper surveys, call in talk-show surveys, etc. |
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| Samples in which the subjects are chosen randomly to be in the sample are often representative of the population and are, for the most part, free of bias. |
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| probability sampling design |
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Definition
| When each subject of the population has a positive and equal probability of being selected for the sample |
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| Stratified Random Sampling |
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Definition
| The population is naturally divided into two or more groups of similar subjects |
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| Multistage Random Sampling |
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Definition
| Instead of randomly selecting subjects from each group (as in stratified sampling), we randomly select (using simple random sampling) several of these groups. |
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Definition
the subjects (or individuals or units)
on which the measurements are
made. |
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Definition
an experimental condition applied to the
experimental units |
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Definition
the characteristic that is measured on each
experimental unit |
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Definition
the group or groups of experimental
units who receive the treatment(s |
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Definition
a group of experimental units who do not
receive the treatment, but instead receive
either a fake treatment or nothing at all |
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Definition
a fake treatment that is given to the experimental
units in the control group to prevent them from
knowing to which group they belong |
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Definition
When there exists some factor other than
the treatment that makes the treatment and
control groups different |
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Definition
The experimenter randomly selects experimental units to be in
the experiment and can control to which group each is assigned. |
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Definition
The experimenter observes the experimental units as they are.
They either cannot or do not control to which group each
experimental unit is assigned.
They do not impose the treatments (or placebo) on the
experimental units. |
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