A case-control study was performed to determine whether head injury was associat

Question

A case-control study was performed to determine whether head injury was associated with an increased risk of brain tumors in children. 200 cases with brain cancer were identified from the state cancer registry and 200 controls were recruited from the same neighborhoods where the cases lived. The mothers of the children completed a questionnaire that asked them to describe their child’s past history of head injury. The investigators found that the mothers of the children with brain tumors reported a past head injury for 70 of the cases while a past history of head injury was reported in 30 of the controls. What type of bias was likely to have influenced the findings of this study, and why? What can be done to minimize this type of bias?

Explanation / Answer

The type of bias is recall bias

Recall Bias

When people remember past events, they don’t usually have a complete or accurate picture of what happened. In fact, it’s been shown that our brains continuously rewrite memories, clouding them with current events, or even editing them completely; five years after an event, 50% of the memories for that event are completely lost.

Here we also ask to patiant mother regarding to past history of child head injury but she may not give the exact ans as it is few year before incident so the ans that given by patiant mother may not be all correct and we get bias their

We can take these precautions to minimised bais in these type of case study

Define your research question carefully. A poorly worded research question can result in poor understanding all around.

Choose and implement an appropriate Data Collection Method.
Devise high quality questionnaires and ensure your interviewers are well trained. Interviewees should be allowed sufficient time for adequate recall of long term memory.

Use a prospective study, which can eliminate reporter bias.

If using a case-control study, use nested case-control designs. With these designs, baseline data is collected as well as periodically.
If studying a disease or condition, choose participants with a new diagnosis if at all possible.
Verify any information given with a reliable third party, medical record or other trustworthy source.

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