Hierachical regression. Unique variance from one factor, model as whole not significant

[rhf21]

Hi,

I carried out a regression analysis on vocabulary and sentence comprehension scores in relation to text comprehension. I only have a small sample size (11) but this study is meant as a pilot so I wanted to attempt a regression.

The model as a whole explains 48.3% of the variance yet it is not significant - F(2,8) = 3.736, P > .05.
Sentence comprehension explains unique variance.  Adjusted R2 = .35, F (2,10) = 8.22, p < .05.

I don't really understand these results. Could someone please help?

Thanks


Becca

[Swank, Paul R]

Vocabulary obviously does not contribute much to the prediction of text comprehension over and above sentence comprehension. I expect they are highly correlated. Drop vocabulary from the model, paying particular attention to the changes in the parameter estimate and the standard error. It might also be useful to look at the individual correlations.

Dr. Paul R. Swank,
Children's Learning Institute
Professor, Department of Pediatrics, Medical School
Adjunct Professor, School of Public Health
University of Texas Health Science Center-Houston


-----Original Message-----
From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of rhf21
Sent: Tuesday, April 17, 2012 12:46 PM
To: [hidden email]
Subject: Hierachical regression. Unique variance from one factor, model as whole not significant

Hi,

I carried out a regression analysis on vocabulary and sentence comprehension
scores in relation to text comprehension. I only have a small sample size
(11) but this study is meant as a pilot so I wanted to attempt a regression.

The model as a whole explains 48.3% of the variance yet it is not
significant - F(2,8) = 3.736, P > .05.
Sentence comprehension explains unique variance.  Adjusted R2 = .35, F
(2,10) = 8.22, p < .05.

I don't really understand these results. Could someone please help?

Thanks


Becca

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