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# ECN225-EXAM1

### ECN225-EXAM1 FURMAN ROE

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

Compare a 'population' to a 'sample'. | Pop = set of all measurements of interestSample = subset of the population |

Compare a 'parameter' to a 'statistic'. | Parameter = a # deduced from the populationStatistic = a # taken from the sample data |

What is the problem with populations/parameters? Or, why do we use samples/statistics more frequently? | Populations and parameters are very difficult to gather. Stats gives us an accurate account of the larger groups information. |

Define 'mean'. | The sum of the observations divided by the # of observations. (average) |

Define 'median'. | The value in the middle of the data set when they are organized lowest to highest. This is averaged when there are two numbers. (middle) |

Define 'mode'. | The value that occurs with the greatest frequency. |

Define and calculate a 'percentile'. | Def - The pth percentile is a value where p percent of all observations are less than or equal to this value. i = (p/100)n, where n is the number of values. 'i' is the i'th number in the ordered list of data. note: the 50th percentile is also the median. |

Calculate the 'quartiles'. | Q1 :: i=(25/100)n , Q2 :: i=(50/100)n , Q3 :: i=(75/100)n |

Calculate 'range'. | largest value - smallest value = range |

Calculate 'Interquartile Range (IQR)'. | IQR = [Q1 - Q3] , Q1 :: i=(25/100)n , Q3 :: i=(75/100)n |

Define the 'variance' and calculate sample variance. | The measure of variability around the mean. Sample variance (denoted as s^2) = (sum of all squared deviations)/(n - 1) where "deviations" is (x'i - mean) |

Define and calculate the 'standard deviation'. | The standard deviation is the positive square root of the variance. |

Calculate the 'coefficient of variation'. | ((standard deviation / mean) x 100)% |

Define and calculate the 'z-score'. | aka 'the standardized value'. The number of standard deviations the value is away from the mean. (x'i - mean)/(sample standard deviation) |

Define 'Chebyshev's Theorem'. | At least (1 - 1/z^2) of the data values must be within z standard deviations of the mean, where z is any value greater than 1. |

Define 'empirical rule'. | *only used when symmetrical, bell-curve distribution* 68% of data is within 1 standard deviation, 95% is within 2 sd, and almost all is within 3 sd. |

Explain how to detect an outlier. | An outlier has a z-score of 3 or more (it is 3 or more standard deviations away from the mean). |

Combinations | --- |

Permeutations | --- |

Draw a Tree Diagram. | ... |

Combinations nCr | |

Define 'Intersection'. | The points belonging to A and B. |

Define 'mutually exclusive'. | Neither A nor B have any similar points. |

Created by:
ksimpson