📚 Repeatable Measurements in A-Level Physics | A-Level物理中的可重复测量
In AQA A-level Physics, practical skills are assessed through written questions that ask you to evaluate data, procedures and errors. One key term is 'repeatable'. Understanding what makes a set of measurements repeatable, and how repeatability differs from similar words like 'reproducible', is essential for the practical-based questions in Papers 3 and 5, and in the required practical endorsement.
在AQA A-Level物理中，实验技能通过书面题目来考查，要求你评估数据、步骤和误差。其中一个关键术语就是 '可重复'。理解什么使一组测量可重复，以及可重复与 '可重现' 等相似词的区别，对于第3卷和第5卷中的实验题以及必修实验考核至关重要。
1. What 'Repeatable' Means in AQA Physics | AQA物理中“可重复”的含义
In AQA physics, a measurement is repeatable if the same experimenter, using the same equipment and the same method, gets the same results when the experiment is repeated over a short time interval. For example, if you measure the time for a pendulum to complete ten swings five times, and the five values are 12.4 s, 12.5 s, 12.4 s, 12.6 s and 12.5 s, the results are repeatable because the spread is small.
在AQA物理中，如果同一位实验者使用相同的设备和相同的方法，在短时间内重复实验得到相同的结果，则该测量是可重复的。例如，如果你测量单摆完成十次摆动的时间五次，五个值分别为12.4 s、12.5 s、12.4 s、12.6 s和12.5 s，则结果可重复，因为数据分布很小。
Repeatability is about consistency, not necessarily correctness. A result can be repeatable even if it is far from the true value because of a systematic error. For instance, a voltmeter with a zero error may give 0.52 V every time for a true 0.50 V. The readings are repeatable but inaccurate.
可重复性关乎一致性，而不一定是正确性。即使结果因系统误差而远离真值，也可能可重复。例如，零误差的电压表对于真值0.50 V可能每次都显示0.52 V。读数可重复但不准确。
2. Repeatable vs Reproducible | 可重复与可重现的区别
AQA expects you to distinguish 'repeatable' from 'reproducible'. A result is reproducible if a different experimenter, using a different technique or different equipment, obtains the same result. Repeatable refers to the same person and same equipment; reproducible refers to different people and often different apparatus or methods.
AQA要求你区分 '可重复' 和 '可重现'。如果不同的实验者使用不同的技术或不同的设备得到相同的结果，则结果可重现。可重复指同一人和同一设备；可重现指不同的人，通常也指不同的设备或方法。
| Repeatable | Reproducible |
| Same experimenter, same equipment, short time | Different experimenter, different equipment or method |
| Tests consistency of one person's method | Tests reliability across independent teams |
The table above summarises the key contrast. In an exam answer, always check whether the question describes the same student repeating the experiment or a different student using different apparatus.
上表总结了关键区别。在考试答案中，一定要检查题目描述的是同一名学生重复实验，还是不同的学生使用不同的设备。
3. Random Errors and Repeatability | 随机误差与可重复性
Random errors cause readings to scatter unpredictably above and below the true value. They are the main limiting factor for repeatability. Sources include human reaction time when starting and stopping a stopwatch, small fluctuations in room temperature, noise in electrical signals, and parallax when reading a scale. If random errors are large, repeated readings show a wide spread, so the results are not repeatable.
随机误差导致读数在真值上下不可预测地波动。它们是限制可重复性的主要因素。来源包括启动和停止秒表的人为反应时间、室温的小幅波动、电信号中的噪声，以及读取刻度时的视差。如果随机误差大，重复读数会显示较大的离散度，因此结果不可重复。
Repeating a measurement and taking the mean reduces the effect of random errors, making the result more reliable. This is why AQA required practicals often ask you to repeat readings and calculate a mean. The mean is the best estimate of the true value when only random errors are present.
重复测量并取平均值可以减小随机误差的影响，使结果更可靠。这就是为什么AQA必修实验经常要求你重复读数并计算平均值。当只存在随机误差时，平均值是对真值的最佳估计。
4. Resolution, Precision and Repeatability | 分辨率、精密度与可重复性
Repeatability is closely related to precision. Precision describes how closely repeated measurements agree with each other. A set of results with a small range is precise, and therefore repeatable. Resolution is the smallest change an instrument can detect, such as 0.01 s on a digital stopwatch or 1 mm on a metre ruler. A finer resolution does not automatically make results repeatable, but it can reveal small variations that a coarser instrument would hide.
可重复性与精密度密切相关。精密度描述重复测量之间的一致性程度。范围小的一组结果是精密的，因此也是可重复的。分辨率是仪器能够检测到的最小变化，例如数字秒表的0.01 s或米尺的1 mm。更精细的分辨率并不自动使结果可重复，但它可以揭示较粗仪器会掩盖的微小变化。
An instrument with poor resolution may make results appear artificially repeatable because all readings are rounded to the same coarse scale division. For example, a thermometer with 1 °C divisions may give 22 °C, 22 °C, 22 °C, but a 0.1 °C thermometer may show 22.1 °C, 22.3 °C, 22.0 °C. The first set looks repeatable but lacks information.
分辨率差的仪器可能使结果看起来人为地可重复，因为所有读数都被四舍五入到相同的粗糙刻度分度。例如，分度为1 °C的温度计可能给出22 °C、22 °C、22 °C，而0.1 °C的温度计可能显示22.1 °C、22.3 °C、22.0 °C。第一组看似可重复，但缺乏信息。
5. How to Assess Repeatability from Data | 如何从数据评估可重复性
bility. You can also quote the uncertainty as half the range, often written as ±(range/2).
在考试题目中，可能会给你重复读数并询问结果是否可重复。回答时，计算极差，即用最大读数减去最小读数。与平均值相比，极差小表明可重复性好。你也可以将不确定度表示为极差的一半，通常写作 ±(极差/2)。
tainty from repeatability is ±0.01 mm, which is small, so the measurements are repeatable.
例如，测量导线直径五次得到0.42 mm、0.41 mm、0.43 mm、0.42 mm、0
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