Solved – Can causality be inferred in a study with an experience followed by two sets of measures

I came across this study as part of a mock exam paper and was confused to say the least.


The study investigates cognitive and behavioural factor related to the experience of anxiety in MRI scanners.

Participants completed the following questionnaires 5 mins after the scan:

  • a measure of the frequency of anxiety experienced in the scanner
  • a measure of the frequency of physical symptoms of panic
  • a measure of the frequency of coping strategy employment
  • a measure of the frequency of claustrophobic-related thoughts

Participants were also asked to fill in and submit general measures at home after the scan:

  • level of claustrophobic fears regarding restriction and suffocation
  • depression
  • anxiety
  • health anxiety

The return rate was 75%, i.e. only 97 of the original 130 participants completed the second batch of questionnaires.

Overall, the level of anxiety in the scanner was RELATED TO:

  • level of claustrophobic fears regarding restriction and suffocation
  • frequency of coping strategy to manage scanner anxiety
  • no. symptoms of panic during the scan
  • no. claustrophobia-related thoughts about the scan.

No stats are given.


  • What type of design is this?
  • Is it possible to understand the causes of anxiety experienced in MRI using this type of design?

Initial Thoughts:

In my mind, causality can not be inferred because there is no comparison with a control group, and correlation would probably have been used rather than AVOVA. Is this the answer to the questions above or have I missed the point?

Best Answer

I think you're on the right track. Before drawing any conclusions about causality, I'd want to know…

…to what degree the 97 were representative of the 130, and the 130, to the population of interest.

…the magnitude of any relationships found as well as their statistical sig. (Whether correlation or anova was used is not, I think, directly relevant to your question.)

…the psychometric properties (validity and reliability indicators) of all measures used (perhaps one would want to adjust for reliability attenuation, for instance).

…what the subjects' characteristics were at baseline, i.e., before undergoing the scanner experience.

…as you've said, how a control group would compare.

The bottom line is, this is a correlational/observational study and, certainly as reported, says little about causal relationships.

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