Variables and Making Measurements | 变量与测量

📚 Variables and Making Measurements | 变量与测量

Reliable biological investigations depend on careful identification of variables and accurate measurement. In A-Level Biology practical work, you must be able to plan experiments, choose appropriate apparatus, record data correctly, and evaluate sources of error. This revision guide explains independent, dependent and control variables, compares accuracy with precision, and gives the key points for making valid measurements.

可靠的生物学实验取决于对变量的准确识别和精确测量。在 A-Level 生物实验操作中，你必须能够设计实验、选择合适的仪器、正确记录数据并评估误差来源。本复习指南解释自变量、因变量和控制变量，比较准确度与精密度，并给出进行有效测量的关键要点。

1. Independent and Dependent Variables | 自变量与因变量

In any biological investigation, the independent variable is the factor that the investigator deliberately changes, while the dependent variable is the factor that is measured as the outcome. For example, when studying the effect of temperature on amylase activity, temperature is the independent variable and the time taken for starch to disappear is the dependent variable.

在任何生物学实验中，自变量是研究者刻意改变的因素，而因变量是作为结果被测量的因素。例如，研究温度对淀粉酶活性的影响时，温度是自变量，淀粉消失所需的时间是因变量。

The independent variable must be given a suitable range and interval, such as 10, 20, 30, 40 and 50 °C, and the dependent variable must be measured with a named piece of apparatus, such as a colorimeter or stopwatch.

自变量必须设定合适的范围和间隔，例如 10、20、30、40 和 50 °C；因变量必须使用指定的仪器测量，如比色计或秒表。

2. Control Variables | 控制变量

Control variables are all the factors that could influence the dependent variable but must be kept constant during the experiment. In the amylase investigation, control variables include enzyme concentration, substrate concentration, pH, volume of starch solution, and stirring method.

控制变量是可能影响因变量、但在实验中必须保持恒定的所有因素。在淀粉酶实验中，控制变量包括酶浓度、底物浓度、pH、淀粉溶液体积和搅拌方式。

If a control variable is not kept constant, the results may be invalid because the cause of any change cannot be attributed solely to the independent variable. A planning table should list each control variable, the exact value or condition used, and how it will be controlled.

如果控制变量未保持恒定，结果可能无效，因为任何变化的原因不能完全归因于自变量。计划表应列出每个控制变量、使用的准确值或条件，以及如何控制它。

3. Control Experiments | 对照实验

A control experiment is a separate setup in which the independent variable is removed or set to a baseline condition. It acts as a standard of comparison. For example, when testing the effect of an antibiotic on bacterial growth, a control plate without antibiotic must be incubated under the same conditions.

对照实验是独立设置的一组，其中自变量被移除或设为基线条件。它可充当比较标准。例如，测试抗生素对细菌生长的影响时，不含抗生素的对照平板必须在相同条件下培养。

Negative controls are expected to show no response, while positive controls are expected to show a known response. Controls help confirm that the method

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