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# elem stats chap 3

### a brief version elementary statistics chap 3

Question | Answer |
---|---|

statistic | a characteristic or measure obtained by using the data values from a SAMPLE. |

parameter | a characteristic or measure obtained by using all the data values for a specific population |

mean | summ of the values divided by the total number of values. (average) |

median | the midpoint of the data. - arrage numbers in order and select the middle point (MD) |

mode | value that occurs most often in a data set |

midrange | the sum of the lowest and the highest values in the data set divided by 2 (MR) |

weighted mean | a type of mean that considers an additional factor by assigning a corresponding weight to each value. multiply the weight by each value then find the sum of all. Then divide by the sum of all weights. |

positively or right skewed distribution | majority of the data fall to the left of the mean. mode/median/mean |

negatively or left skewed distribution | majority of data values fall to the right of the mean and cluster at the upper end. mean/median/mode |

range | highest value minus the lowest value. (R) |

variance | average of the squares of the distance each value is from the mean (lowercase sigma) |

standard deviation | the square root of the variance. |

coefficient of variation | the standard deviation divided by the mean. Expressed as a percentage. |

Chebyshev's Theorem | proportion of values from a data set that will fall within k standard deviations of the mean will be at least 1-1/k2 |

symetrical distribution | data values are evenly distributed on bothe sides of the mean. the mean median and mode may be the same value. (standard bell curve) |

empirical rule | when the distribution in "normal" or bell shaped - 68% of data fall within one Standard deviation, 95% fall within two standard deviations and 99.7% fall within three standard deviations. |

standard score or z score | subtract the mean from the value and divide by the standard deviation. - represents the number of standard deviations a data value falls above or below the mean. |

percentiles | used in education and health related fields to indicate the position of an individual in a group. divides the data set into 100 equal groups. |

quartile | dividing the distribution into four groups |

decile | dividing the distribution into ten groups |

outlier | and extremely high or an extremely low data value when compared with the rest of the data values. (calculated by multiplying the the interquartile range by 1.5 and adding to the upper quartile or subtracting from lower quartile) |

interquartile range | the range between the upper quartile and the lower quartile. (subtract lower quartile value from upper quartile value) |

stem and leaf plot | a data chart the uses part of the data value (often the tens place value) in the stem column and another part of the value (the ones place value) in the other column |

box plot | data arranged in a line plot centered around five specific values. (minimum value, Q1, median, Q3, maximum value) called five-number summary. |

resistant statistic | statistic that is relatively less affected by outliers than others. (ex. median and interquartile range) |

nonresistant statistic | statistic that is relatively more affected by outliers. (ex. mean and standard deviation) |

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newbytutor