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Validity of the Bread Investigation
For each of three bread types, the student put a square piece into their mouth, did not chew it and recorded the time taken for the bread to taste sweet.
Suggest one reason why the results of the investigation were not valid.
Do not refer to control variables in your answer.
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Marking points
- 1 Gives one accepted validity limitation that is not a control-variable issue.
Full-mark answer
The judgement of when the bread tastes sweet is subjective, so the measured time depends on the student's perception.
Why this answer loses marks
They did not calculate a mean.
The mark scheme ignores this; identify a non-control flaw such as repeatability, subjective taste or variable saliva.