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# Stats Vocab Ch. 1

### Sullivan Statistics - Informed Decisions Using Data

Term | Definition |
---|---|

statistics | The science of collecting, organizing, summarizing, and analyzing information to draw conclusions or answer questions. In addition, statistics is about providing a measure of confidence in any conclusions. |

data | Facts or propositions used to draw a conclusion or make a decision. The list of observed values for a variable. |

population | The entire group of individuals to be studied. |

individual | A person or object that is a member of the population being studied |

sample | A subset of the population that is being studied. |

statistic | A numerical summary of a sample. |

descriptive statistics | Consists of organizing and summarizing data. Describe data through numerical summaries, tables, and graphs. |

inferential statistics | Uses methods that take a result from a sample, extend it to the population, and measure the reliability of the result. One goal is to estimate parameters. |

parameter | A numerical summary of a population. |

the process of statistics | 1. Identify the research objective 2. Collect the data needed to answer the question(s) posed in step 1 3. Describe the data 4. Perform inference |

convenience samples | Samples obtained through convenience rather than systematically, i.e. Internet or phone-in polls. Not based on randomness. Not considered reliable. |

variables | The characteristics of the individuals within the population. |

qualitative variables | Allow for classification of individuals based on some attribute or characteristic - sometimes called categorical variables. |

quantitative variables | Provide numerical measures of individuals. Math operations such as addition and subtraction can be performed on the values of a quantitative variable and will provide meaningful results. |

discrete variable | A quantitative variable that has either a finite number of possible values or a countable number of possible values. The values result from counting. |

continuous variable | A quantitative variable that has an infinite number of possible values that are not countable, but are instead measured. |

observational study | Measure the value of response variable w/out trying to influence the value of the response or explanatory variables. Researcher observes behavior of individuals in the study w/out trying to influence outcome. Association may be claimed but not causation. |

designed experiment | An experiment where the researcher assigns the individuals in a study to a certain group, intentionally changes the value of an explanatory variable, then records the value of the response variable for each group. |

explanatory variable | A variable that explains or causes changes in the response variable - sometimes called the predictor variable. |

response variable | A variable that measures an outcome or result of a study (variable whose changes are to be studied). |

confounding variable | An explanatory variable that was considered in a study whose effect cannot be distinguished from a second explanatory variable in the study. |

lurking variable | An explanatory variable that was not considered in a study, but that affects the value of the response variable in the study. Lurking variables are typically related to explanatory variables considered in the study. |

census | A list of all individuals in a population along with certain characteristics of each individual. |

random sampling | The process of using chance to select individuals from a population to be included in the sample. |

simple random sampling | Every possible sample of size n from a population of size N has an equally likely chance of occurring. |

frame | Lists all the individuals in a population. |

stratified sample | Obtained by separating the population into non-overlapping groups (called strata) and then obtaining a simple random sample from each stratum. The individuals within each stratum should be homogeneous in some way. |

systematic sample | Obtained by selecting every kth individual from the population. The first individual selected corresponds to a random number between 1 and k. |

cluster sample | Obtained by selecting all individuals within a randomly selected collection or group of individuals. |

bias | The results of the sample are not representative of the population. |

sampling bias | The technique used to obtain the individuals in the sample tends to favor one part of the population over another, and results due to undercoverage. |

nonresponse bias | When individuals selected in the sample who do not respond to the survey have different opinions from those who do respond to the survey. |

response bias | When the answers on a survey do not reflect the true feelings of the respondent. |

control group | Serves as a baseline treatment that can be used to compare it to other treatments. |

placebo | Is a treatment that looks just like the "real" treatments in the study. |

single-blind experiements | An experiment in which the experimental unit (subject) does not know which treatment he or she is receiving. |

double-blind experiments | An experiment in which neither the experimental unit (subject) nor the researcher in contact with the experimental unit knows which treatment the experimental unit is receiving. |

treatment | Any combination of the values of the factors in an experiment. |

experimental unit (subject) | A person, object, or some other well-defined item upon which a treatment is applied. |