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# WGU RFC 1 ch 8

### Summary of Chapter 8

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

Correlational research | involves collecting data to determine whether and to what degree a relations exists between two or more variables |

degree of relation | is expressed as correlation coefficient |

If two variables are related | scores within a certain range on one variable are associated with scores within a certain range on the other variable |

Relation between variables | does not imply that one is the cause of the other |

not infer causal relations | on the basis of data from a correlational study |

correlational studies | may be designed either to determine whether and how a set of variables are related or to test hypotheses regarding expected relations. |

Variables to be correlated | should be selected on the basis of some rationale suggested by theory or experience |

common, minimally accepted sample size for a correlational study | 30 participants |

variables correlated have low reliabilities and validities | a bigger sample is necessary |

Basic correlational design, scores for two (or more) variables of interest | are obtained for each member of a selected sample, and the paired scores are correlated. |

A correlation coefficient is a decimal number between | -1.00 and +1.00. It describes both the size and direction of the relation between two variables |

If correlation coefficient is near | .00, the variables are not related |

A correlation coefficient is near | +1.00 indicates that the variables are strongly and positively related. An increase on one variable is associated with an increase on the other |

If the correlation coefficient is near | -1.00, the variables are strongly and negatively or inversely related. An increase on one variable is associated with a decrease on the other variable |

Correlations of +1.00 and -1.00 | represent the same strength but different directions of relation |

A correlation coefficient much lower than .50 is | generally not useful for group prediction or individual prediction. |

However a combination of correlations below .50 | may yield useful prediction |

Coefficients in the .60s and .70s | are usually considered adequate for group prediction purposes |

Coefficients in the .80s and higher | are adequate for individual prediction purposes |

Common variance or share variance | indicates the extent to which variables vary in a systematic way |

the higher the common variance | the higher the correlation |

Statistical significance | refers to the probability that the study results (e.g., correlation coefficient of this size) would have occurred simply due to chance |

Small samples require | larger correlation coefficients to achieve significance |

the value of the correlation coefficient needed for significance | increases as the level of confidence increases |

A low coefficient represents | a low degree of association between variables, regardless of statistical significance |

relationship study | conducted to gain insight into the variables or factors that are related to a complex variable, such as academic achievement, motivation, or self concept |

in a relationship study, the researcher | first identifies the variables to be related |

Prediction study | is an attempt to determine which of a number of variables are most highly related to the criterion variable |

Prediction studies | are often conducted to facilitate decision making about individuals or to aid in the selection of individuals. |

Variable used to predict | predictor |

variable that is predicted is | complex variable, called the criterion |

Data analysis in prediction studies | involve correlating each predictor variable with the criterion variable |

prediction study using multiple variables | results in a prediction equation referred to as a multiple regression equation, which combines all variables that individually predict the criterion to make more accurate prediction. |

Created by:
Xyrarose