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# Statistics

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

qualitative | observations about data made by using your senses |

quantitative | observations about data made by using tools |

statistic | a piece of numerical data |

statistical question | a question that can be answered by collecting quantitative data that will vary |

variability | the measure of the spread of a data set |

natural variability | differences that occur in a data set because of a natural system |

measurement variability | differences that occur in a data set because of user error |

sample variability | differences that occur in a data set because of a different sample or set |

stem-and-leaf plot | a method to display the frequency of a value in a set of data |

histogram | a method to display groups of data in a set of data |

mean absolute variation | a method to display how far from the mean each data point (on average) is |

5-number summary | a method to display data points in a set used to create a boxplot |

symmetrical | data that, when graphed, are evenly distributed around the mean |

bimodal | data that, when graphed, have two clusters on each end of the graph |

skewed | data that, when graphed, have one cluster at either end of the graph |

spread | a method to display how far apart data points are in a set (measured by range) |

dispersion | a method to display how far apart data points are is a set (also known as spread) |

cluster | a group of data that is close together in a set of data |

outlier | a data point in a set of data that is at least 1.5 times smaller than Q1 -OR- at least 1.5 times larger than Q3 |

boxplot | a method to organize, summarize, and display data in a set of data |

first quartile | a statistic in a boxplot describing the lowest portion of data (also known as Q1 or lower quartile) |

third quartile | a statistic in a boxplot describing a portion of data (also known as Q3 or upper quartile) |

interquartile range | a statistic in a boxplot describing the range between Q3 and Q1 (also known as IQR) |

whiskers | data points in a boxplot that do not fall within the IQR (these are the minimum and maximum data points) |

range | the difference between the largest and smallest data points in a set of data (this is the measure used to describe spread or dispersion) |

average | the calculated central value of a set of data (also known as mean) |

mean | the calculated central value of a set of data (also known as average) |

median | the middle number in a data set that has been written in numerical order |

centering point | the middle number in a data set that has been written in numerical order (also known as median) |