The following scatterplot represents the results of a study undertaken by Chakrabarty et al. (2005) who were investigating glutamate levels in psychotropic drug-naive OCD patients and comparing them with psychiatrically normal controls. Based on this scatterplot the following ANCOVA of glutamate levels in CSF was done. Findings were reported as follows for CSF glutamate levels in OCD patients compared to controls: F(1,29)=11.153, p=0.002. What conclusion can be drawn about this result? Scatterplot showing CSF glutamate levels in patients (1) and controls (2).
ANCOVA of Glutamate Levels in CSF
Diagnosis (OCD vs Controls) and gender were included as factors, while age, number of years of illness, total Y-BOCS scores, and CGI-S scores were included as covariates in the analysis.
A) A significant main effect of gender is evident on CSF glutamate levels.
B) A significant main effect of age is evident on CSF glutamate levels.
C) A significant main effect of diagnosis is evident on CSF glutamate levels.
D) No significant effects are evident on CSF glutamate levels.

Question

The following scatterplot represents the results of a study undertaken by Chakrabarty et al. (2005) who were investigating glutamate levels in psychotropic drug-naive OCD patients and comparing them with psychiatrically normal controls. Based on this scatterplot the following ANCOVA of glutamate levels in CSF was done. Findings were reported as follows for CSF glutamate levels in OCD patients compared to controls: F(1,29)=11.153, p=0.002. What conclusion can be drawn about this result?  Scatterplot showing CSF glutamate levels in patients (1) and controls (2).
ANCOVA of Glutamate Levels in CSF
 Diagnosis (OCD vs Controls) and gender were included as factors, while age, number of years of illness, total Y-BOCS scores, and CGI-S scores were included as covariates in the analysis.
A) A significant main effect of gender is evident on CSF glutamate levels. 
B) A significant main effect of age is evident on CSF glutamate levels. 
C) A significant main effect of diagnosis is evident on CSF glutamate levels. 
D) No significant effects are evident on CSF glutamate levels.

Quizplus · Accepted Answer

The ANCOVA analysis found a significant main effect for diagnosis (OCD vs controls) on CSF glutamate levels, with a high F-value and a low p-value, indicating that the difference between the two groups is unlikely to have occurred by chance. No significant main effect was found for gender or age.

The Following Scatterplot Represents the Results of a Study Undertaken