WBI13Topic 3.23 questions
Variables, controls, sample sizes, reliability and validity of investigations.
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Original practice questions written in the style of the exam.
A student investigates the effect of caffeine concentration on the heart rate of Daphnia (water fleas).
Describe four variables that should be controlled, and explain why one of them must be controlled.
A student investigates how enzyme concentration affects the rate at which trypsin breaks down the protein in milk. She sets up an extra tube containing milk and boiled trypsin.
Explain the purpose of this tube and why she should carry out three repeats at each concentration.