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# WGU RFC 1 ch 12

### Summary of Chapter 12

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

Formulas for statistical procedures are | just basic mathematical procedures |

first step toward analysis | involves converting behavioral responses into some numeric system or categorical organization |

Frequency | refers to the number of times something occurs; with descriptive statistics |

Nominal or ordinal variables | frequency count by each value is very descriptive |

frequency | is more complicated for interval or ratio variables |

Measures of central tendency | indices that represent a typical score among a group of scores |

mean | arithmetic average of the scores, most frequently used measure of central tendency; appropriate for describing interval or ratio data |

median | midpoint in a distribution; 50% of the scores are above the median, and 50% are below the median; most useful when looking at ordinal variables or data sets in which the scores vary widely over distribution |

mode | score that is attained by more subjects than any other score (i.e., occurs most frequently); a set of course may have two or more modes; when nominal data are collected, the mode is the only appropriate measure of central tendency |

two sets of data that are very different can have identical means or medians | creating a need for measures of variability, indices that indicate how spread out a group of scores are |

the range | simply the difference between the highest and lowest score in a distribution and is determined by subtraction |

quartile deviation | one half of the difference between the upper quartile (75th percentile) and the lower quartile (25 percentile) in a distribution |

quartile deviation | more stable measure of variability than the rand and is appropriate whenever the median is appropriate |

variance | defined as the amount spread among scores, if the variance is small the scores are close together, if it is large, the scores are more spread out |

standard deviation | square root of the variance of a set of scores; it is the most stable measure of variability and takes into account every score |

when plotted as a frequency graph a normal distribution forms a bell shape | normal curve |

when distribution is not normal | it is said to be skewed, there are more extreme scores at one end than the other |

negatively skewed | the extreme scores are at the lower end of the distribution |

positively skewed | the extreme scores are at the upper or higher end of the distribution |

percentile rank | indicates the percentage of scores that fall at or below a given score |

percentiles | are appropriate for data measured on an ordinal scale |

standard score | reflects how many standard deviations a students score is above or below the mean |

T score | z score transformed to eliminate pluses or minuses |

measures of relationship | indicate the degree to which two sets of scores are related |

degree of relationship | expressed as a correlation coefficient, which is computed from two sets of scores from a single group of participants |

Pearson r | most appropriate measure of correlation when the sets of data to be correlated are expressed as either interval or ratio scales |

Pearson r | not valid if the relation between variables is not linear |

Spearman rho | appropriate measure of correlation when the variables are expressed as ranks |

Created by:
Xyrarose