When Considering Correlations.. « phd monkey

phd monkey An expedition through the forest of academia.

13Jul/11

When Considering Correlations..

When considering correlations, they are descriptive in that they demonstrate relationship between variables: positive, negative, none.
But correlations are also used in inferential statistics, so we can infer what we find in our sample accurately represents what would be seen in the larger population.

1. If two variables, we ask is the level of measurement (of the data) nominal or ordinal?
a. If yes, we use those statistics you listed below ("Point-biserial (rpbi), Spearman rank-order (rs ), Phi (Φ), Gamma (γ)" and Kendall's tau
b. If no, for interval or ratio, we use Pearson's

2. If more than two variables, we ask again what is the level of measurement?
a. For Nominal or ordinal level, we use Logistic regression
b. For Interval or ratio levels, we use Multiple regression, Path analysis.

So..
When research asks for relationship and..

When there are 2 Variables and..
The level of measurement is: nominal or ordinal we use:

  • Point-biserial (rpbi)
  • Spearman rank-order (rs ),
  • Phi (Φ)
  • Gamma (γ)
  • Kendall's tau

When there are 2 Variables and..
The level of measurement is interval or ratio we use:

  • Pearson's r

When there are More Than 2 Variables and..
The level of measurement is: nominal or ordinal we use:

  • Logistic regression

When there are More Than 2 Variables and..
The level of measurement is interval or ratio we use:

  • Multiple regression
  • Path analysis.

Steinberg, W. J. (2011). Statistics alive (2nd ed.). Thousand Oaks, CA: Sage Publications.

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