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Controlling reaction-time investigations
Scientists investigated whether blood glucose concentration affects reaction time. The reaction times of ten people with Type 1 diabetes were measured. This is the method used.
- Tell one person to drink a glucose solution.
- Monitor the person’s blood glucose concentration.
- Record the person’s reaction time when the person’s blood glucose concentration is 16 mmol/dm³, 6 mmol/dm³ and 3 mmol/dm³.
- Repeat steps 1 to 3 for the nine other people.
Suggest two other control variables that should be used in the investigation.
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Marking points
- 1 Controls prior familiarity or practice with the reaction-time test.
- 2 Controls the reaction-time test type or procedure.
- 3 Controls insulin injections.
- 4 Controls an accepted named drug that affects reaction time.
- 5 Controls amount of sleep or tiredness.
- 6 Controls distractions.
Full-mark answer
1. Use the same reaction-time test and the same hand for every person. 2. Control how much sleep each person had before the test.
Why this answer loses marks
Keep health, caffeine and alcohol the same.
Unqualified health is ignored, and caffeine or alcohol is not credited here; name two specific confounders not already controlled in the prompt.