Biology Year 2 Experimental Design | A2生物实验设计

📚 Biology Year 2 Experimental Design | A2生物实验设计

In Year 2 of A-Level Biology (A2), experimental design becomes more sophisticated, requiring you not only to plan valid investigations but also to select appropriate statistical tests, evaluate data critically, and discuss ethical implications. Mastering experimental design is essential for high marks in practical assessments and written examinations.

在A-Level生物学二年级（A2阶段），实验设计的要求更加深入，你不仅需要规划有效的探究活动，还要选择合适的统计检验、批判性地评估数据并讨论伦理问题。掌握实验设计对于实践评估和笔试获得高分至关重要。

1. The Scientific Method and Hypothesis Testing | 科学方法与假设检验

Experiments begin with an observation and a question. You then formulate a testable null hypothesis (H₀) that states there is no effect or no difference, and an alternative hypothesis (H₁) that suggests a significant effect or relationship exists.

实验始于观察和问题。然后你需要提出一个可检验的原假设 (H₀)，陈述没有效应或没有差异，以及一个备择假设 (H₁)，表明存在显著效应或关系。

For example, investigating the effect of light intensity on the rate of photosynthesis: H₀: Light intensity has no effect on the rate of oxygen production. H₁: Light intensity does affect the rate of oxygen production.

例如，研究光照强度对光合作用速率的影响：H₀：光照强度对氧气产生速率没有影响。H₁：光照强度对氧气产生速率有影响。

2. Key Principles: Control, Randomisation and Replication | 核心原则：对照、随机化与重复

Three pillars ensure reliable experiments: control of variables, randomisation of sample assignment, and sufficient replication. The control group allows comparison; randomisation reduces bias; replication gives an estimate of variability.

三个支柱确保实验可靠：变量的控制、样本分配随机化和充分的重复。对照组用于比较；随机化减少偏差；重复提供了对变异性的估计。

In a drug trial, a placebo is a negative control, while a known effective drug can serve as a positive control. Randomly allocating subjects to treatment groups prevents selection bias.

在药物试验中，安慰剂作为阴性对照，而已知有效药物可作为阳性对照。将受试者随机分配到处理组可以防止选择偏倚。

3. Variables: Independent, Dependent and Controlled | 变量：自变量、因变量与控制变量

The independent variable (IV) is what you change; the dependent variable (DV) is what you measure; controlled variables are kept constant to ensure

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