📚 Year 11 Cambridge Psychology: Key Points for Experimental/Practical Assessment | 剑桥 Year 11 心理学：实验/实践考核要点
Mastering the experimental or practical component of Cambridge IGCSE Psychology requires more than memorising core studies. You must be able to design, evaluate, and suggest improvements for psychological investigations. Whether you are sitting the Research Methods paper (Paper 2 for 0990) or the Alternative to Coursework (Paper 3), the examiner assesses your understanding of variables, controls, ethics, data handling, and methodological rigour. This guide walks you through the essential topics that regularly appear in Year 11 assessments, giving you a clear, bilingual overview to boost your confidence and your grade.
要攻克剑桥 IGCSE 心理学的实验或实践考核，光记住核心研究是不够的。你必须能够设计、评估并提出改进心理学调查的方案。无论你参加的是研究方法试卷（0990 大纲的 Paper 2）还是替代课程作业（Paper 3），考官都在检验你对变量、控制、伦理、数据处理与方法严谨性的理解。本指南将带你逐一攻克 Year 11 考试中高频出现的核心专题，以清晰的双语讲解为你理清思路，提升信心与成绩。
1. Understanding Variables: IV, DV and Controls | 理解变量：自变量、因变量与控制变量
The independent variable (IV) is the factor the researcher deliberately manipulates or changes. The dependent variable (DV) is what the researcher measures; it should change as a result of the manipulation. In an experiment testing whether noise affects concentration, the IV might be the level of noise (high vs. low), and the DV could be the number of correct answers on a cognitive task. All other variables that could influence the DV must be controlled, otherwise they become confounding variables that ruin internal validity.
自变量（IV）是研究者有意操纵或改变的因素。因变量（DV）是研究者测量的结果，它会因为自变量的操纵而发生变化。在一个探究噪音是否影响专注力的实验中，IV 可能是噪音强度（高与低），DV 则可以是认知任务中的正确答题数。所有其他可能影响 DV 的变量都必须控制住，否则它们就会成为混淆变量，破坏实验的内部效度。
Operationalising variables means stating them in a precise, measurable way. Instead of saying ‘aggression’, operationalise it as ‘number of times a participant hits a punch bag in 5 minutes’. Clear operationalisation makes your investigation replicable and allows other researchers to check your findings. In practical exams, marks are often lost because candidates fail to provide specific, quantified definitions for both IV and DV.
操作化定义就是把变量用精确、可测量的方式表达出来。不要只说“攻击性”，而要将其操作化为“参与者在 5 分钟内击打沙袋的次数”。清晰的操作化能让你的研究可被重复，也便于其他研究者检验你的发现。在实践考核中，考生常因未能给出自变量和因变量的具体、量化的定义而丢分。
2. Formulating Hypotheses: Null and Alternative | 提出假说：零假说与备择假说
A hypothesis is a testable statement predicting the relationship between variables. The alternative (or experimental) hypothesis states that there will be a difference or a relationship, and it can be directional (one-tailed) or non-directional (two-tailed). For instance, a one-tailed hypothesis might be: ‘Participants in the silent condition will recall significantly more words than those in the noisy condition.’ A two-tailed version would simply predict a difference without specifying direction.
假说是一个可检验的陈述，对变量间的关系作出预测。备择假说（也称实验假说）声称会存在差异或关联，又分为定向假说（单尾）和非定向假说（双尾）。例如，定向假说可以是：“安静条件下的参与者将比噪音条件下的参与者回忆出显著更多的词语。”而非定向假说则只预测有差异，不指明方向。
The null hypothesis always states that there will be no significant difference or relationship, and that any observed effect is due to chance. In practical assessments you are often asked to write a suitable null hypothesis for an investigation. Remember: the null hypothesis is the basis for statistical testing, and learning to phrase it correctly is a key skill.
零假说永远声称不存在显著差异或关联，任何观察到的效应都是随机造成的。在实践考核中，你经常会被要求为一个研究写出合适的零假说。请记住：零假说是统计检验的基础，学会正确表述是一项关键技能。
3. Experimental Designs: Independent Groups, Repeated Measures and Matched Pairs | 实验设计：独立组、重复测量与配对组
In an independent groups design, different participants take part in each condition of the IV. The main advantage is that order effects (such as practice or fatigue) are avoided. However, this design requires more participants and can be weakened by individual differences between groups. Random allocation to conditions helps distribute these differences evenly.
在独立组设计中，参与者在 IV 的每一个实验条件下都是不同的人。其主要优点是可以避免顺序效应（如练习效应或疲劳效应）。但这一设计需要更多参与者，而且组间的个体差异可能会削弱实验效果。将参与者随机分配到不同条件有助于均衡这些差异。
A repeated measures design uses the same participants in all conditions. This controls for individual differences perfectly, but it introduces order effects. Counterbalancing – where half the participants experience condition A first and the other half experience condition B first – can minimise this problem. In an exam you might be asked to suggest why a repeated measures design would be unsuitable for a particular study, for example where a deception is used that cannot be revealed twice.
重复测量设计在所有实验条件下使用同一批参与者。它完美地控制了被试间的个体差异，但会引入顺序效应。平衡设计法——让一半参与者先接受条件 A，另一半先接受条件 B——可以最大限度减少这个问题。考试中可能会问你，为什么重复测量设计不适合某项具体研究，比如研究使用了无法第二次透露的欺骗手段。
Matched pairs design involves recruiting pairs of participants who are similar on key characteristics (e.g., IQ, age) and then splitting them across conditions. It reduces participant variables without introducing order effects, but it is time-consuming and difficult to match participants perfectly. When evaluating designs, always link the strength or limitation back to the specific investigation described in the question.
配对组设计是先招募在关键特征（如智商、年龄）上相似的配对参与者，再将每对分入不同条件。此法能减少被试个体差异，又不引入顺序效应，但既耗时又难以做到完美匹配。评估实验设计时，永远要把优点或局限性与题目所描述的具体研究联系起来。
4. Sampling Methods and Their Limitations | 抽样方法及其局限性
The sample is the group of people who actually take part in a study, drawn from a target population. Random sampling gives every member of the population an equal chance of being selected, drawing names from a hat or using a random number generator. It should produce a representative sample, but it can still be unrepresentative by chance, especially with small samples.
样本是实际参加研究的一组人，它来自目标人群。随机抽样让人群中的每个成员都有均等的机会被选中，比如从帽子里抽名字或使用随机数生成器。理论上这应产生代表性样本，但小样本仍可能因偶然因素而不具代表性。
Opportunity sampling uses people who are readily available, such as friends or passers-by. It is quick and convenient, but highly likely to produce a biased sample. Stratified sampling involves identifying subgroups within the population and then randomly selecting from each in proportion to their occurrence. It is more representative but requires detailed knowledge of the population’s composition. In a practical assessment, you must be prepared to identify the sampling method from a description and suggest one improvement, e.g., changing from opportunity to stratified to increase representativeness.
机会抽样选用身边容易接触到的人，如朋友或路人，便利快捷但极可能产生有偏样本。分层抽样先确定人群中的子群体，再按比例从各层中随机选取。这一方法代表性更强，但需要详细了解人群构成。实践考核中，你必须能根据描述识别抽样方法，并给出改进建议，例如将机会抽样改为分层抽样以提高代表性。
5. Controlling Extraneous Variables | 控制额外变量
Extraneous variables are any variables other than the IV that could affect the DV. If they are not controlled, they become confounding variables and make it impossible to establish a clear cause-and-effect relationship. Common extraneous variables include situational variables (lighting, noise, time of day) and participant variables (mood, motivation, prior knowledge).
额外变量是除了 IV 之外任何可能影响 DV 的变量。如果不加控制，它们就会变成混淆变量，导致无法建立清晰的因果关系。常见的额外变量有情境变量（光线、噪音、一天中的时段）和参与者变量（情绪、动机、先前知识）。
Standardisation is the key strategy: keep the experimental environment, instructions, and materials exactly the same for all participants. Wherever possible, use randomisation to spread out the influence of uncontrolled variables evenly across conditions. For example, randomly allocating participants to conditions helps control for participant variables. In experimental skills questions, always identify one concrete extraneous variable and explain exactly how you would control it.
标准化的程序是关键策略：确保实验环境、指导语、材料对所有参与者都完全一致。尽可能使用随机化手段，让未受控制的变量的影响均匀分布在各实验条件下。例如，随机分配参与者可以控制参与者变量。在实验技能题中，一定要明确指出了一个具体的额外变量，并精确说明你如何控制它。
6. Ethical Guidelines in Psychological Research | 心理学研究中的伦理准则
All psychological investigations must respect the ethical principles of informed consent, right to withdraw, protection from harm, confidentiality, and debriefing. Before taking part, participants (or their guardians) should be given enough information to make an informed decision about participation. They must also know they can stop at any time without penalty.
所有心理学调查都必须遵守知情同意、退出权利、免受伤害、保密和事后解释等伦理原则。在参与之前，应给予参与者（或监护人）足够信息以便作出知情的决定。他们还必须知道自己可以在任何时候无理由退出，不会受到任何惩罚。
Deception should be avoided, but if it is absolutely necessary for the study’s validity, you must justify it and provide a full debrief afterwards. Confidentiality means participants’ personal data must not be shared in a way that identifies them. In an assessment, you might be given an unethical procedure and asked to suggest how to make it more ethical, such as by introducing a consent form, using anonymised codes instead of names, or adding a thorough debrief.
欺骗应尽量避免，但如果对研究效度绝对必要，就必须给出正当理由并在事后进行全面的事后解释。保密原则意味着参与者的个人资料不能以可识别身份的方式公开。考核中你可能会遇到不道德的研究方案，被要求提出改进建议，如引入同意书、使用匿名编码代替姓名、或增加详尽的事后解释。
7. Data Collection Techniques | 数据收集技术
Observations, questionnaires, and interviews are popular non-experimental methods, but you must be ready to evaluate their suitability for a given investigation. Structured observations use coding schemes or tally charts, making numerical data easier to analyse; unstructured observations provide richer qualitative detail but may suffer from observer bias. Inter-observer reliability can be checked by having two observers code the same behaviours independently.
观察法、问卷调查法和访谈法是常见的非实验方法，你需要能够评估它们是否适合一项特定的研究。结构化观察使用编码方案或计数表，易于生成可分析的数字数据；非结构化观察提供更丰富的质性细节，但可能受到观察者偏见的影响。通过让两名观察者独立编码相同的行为，可以检验观察者信度。
Questionnaires can collect a large amount of data quickly, but they rely on self-report, which may be distorted by social desirability bias. Open questions generate detailed, qualitative responses; closed questions produce quantitative data that are easier to compare. In a practical exam, you might need to design a few questions for a study and justify your choice between open and closed formats.
问卷调查能快速收集大量数据，但它依赖自我报告，可能受到社会赞许性偏见的影响。开放式问题产生详细的质性回答；封闭式问题则产生更容易比较的定量数据。实践考试中，你可能需要为一项研究设计几个问题，并论证你选择开放或封闭形式的理由。
8. Descriptive Statistics and Data Presentation | 描述统计与数据呈现
Measures of central tendency (mean, median, mode) summarize the typical value in a data set. The mean uses all values but is sensitive to outliers; the median is unaffected by extreme scores and is better for skewed data. You must be able to calculate these by hand and justify your choice of measure. Measures of dispersion, such as the range and standard deviation, tell you about the spread of the data.
集中趋势量数（平均数、中位数、众数）概括数据集的典型值。平均数用到了所有数据值，但极易受异常值影响；中位数不受极端分数干扰，更适合偏态数据。你必须能手工计算这些量数，并论证自己选择使用哪个。离散量数，如全距和标准差，则说明数据的分散程度。
Data presentation includes bar charts, histograms, and scatter graphs. A bar chart is used for discrete or categorical data, while a histogram is for continuous data. Scatter graphs illustrate correlations. Always label axes fully, give the graph a clear title, and use appropriate, evenly spaced scales. In Paper 3 and Paper 2, you may be asked to plot data or interpret a given graph – marks are invariably given for accurate plotting and correct labelling.
数据呈现包含条形图、直方图和散点图。条形图适用于离散或类别数据，直方图则适用于连续数据。散点图展示相关关系。记得给坐标轴完整标注，给图表清晰标题，并使用恰当且间距均匀的标尺。在 Paper 3 和 Paper 2 中，你可能需要绘制数据或解读已有图表——精确的绘制和正确的标注往往是得分点。
9. Reliability and Validity of Findings | 研究结果的信度与效度
Reliability refers to the consistency of a measurement. If you repeat the procedure under the same conditions, will you get similar results? Test-retest reliability and inter-observer reliability are common checks. Validity asks whether your study actually measures what it intends to measure. Internal validity is high when the only systematic difference between conditions is the IV; external validity concerns how well the findings generalise to other people and settings.
信度指的是测量的一致性。如果你在相同条件下重复实验流程，会得到相似的结果吗？重测信度和观察者信度是常用的检验手段。效度则关注研究是否真正测量了它想测量的东西。当不同条件之间唯一的系统性差异就是 IV 时，内部效度就高；外部效度则关乎研究结果能否推广到其他人群和场景。
Ecological validity, a form of external validity, asks whether the task and setting reflect real-life situations. A laboratory memory test may lack ecological validity because memorising word lists is not a typical everyday activity. To improve validity, researchers can use more natural tasks, such as remembering a shopping list or recalling a story. Candidates should always explain a validity problem concretely and then propose a feasible, clearly described improvement.
生态效度是外部效度的一种，探究实验任务和场景是否反映真实生活。实验室记忆测验可能缺乏生态效度，因为记忆单词表并不是典型的日常活动。为提高效度，研究者可采用更自然的任务，如记忆购物清单或复述故事。考生一定要具体说明效度问题，然后提出切实可行、描述清晰的改进方案。
10. Writing a Lab Report: Structure and Style | 撰写实验报告：结构与风格
A standard psychological report follows APA style and includes the following sections: Abstract, Introduction, Method, Results, Discussion, and References. In the Method section you must describe the design, participants, apparatus/materials, and procedure with enough detail for replication. The Results section presents descriptive statistics and often includes a graph or table, while the Discussion interprets the findings and relates them back to the hypothesis and background literature.
标准的心理学报告遵循 APA 格式，包括摘要、引言、方法、结果、讨论和参考文献。在方法部分，你必须详细说明设计、参与者、仪器/材料与流程，足以让其他人复制实验。结果部分呈现描述统计，通常包含图表；讨论部分则解释研究发现，并将其与假说和背景文献联系起来。
In the alternative-to-practical paper, you may be asked to write parts of a method or to evaluate a given method section. Marks are awarded for correct use of technical vocabulary – for example, referring to ‘participants’ rather than ‘subjects’, and specifying the experimental design clearly. Precision and clarity win marks, so avoid vague phrases like ‘we asked them some questions’ and instead state the exact questions and response format.
在替代实践试卷中，你可能需要撰写方法部分的某些片段，或评价给出的方法部分。正确使用术语是得分点——例如，使用“参与者”而非“被试”，并清楚说明实验设计。精准与清晰才能得分，避免“我们问了一些问题”这类模糊表述，而应写出确切的问题及其回答形式。
11. Common Pitfalls and How to Improve Your Investigation | 常见错误与改进研究的方法
One of the most frequent errors in Year 11 practical work is failing to operationalise the DV properly. Stating that ‘memory was measured’ is insufficient; you must specify the memory test used and the scoring system. Another common mistake is ignoring order effects when using a repeated measures design. Simply stating that order effects were ‘controlled by counterbalancing’ is not enough – you need to describe how counterbalancing was implemented.
Year 11 实践作业中最常见的错误之一就是没有恰当地操作化因变量。只说“记忆力被测量”是不够的；你必须指明所采用的记忆测试类型和评分系统。另一个常见错误是使用重复测量设计时忽略顺序效应。单单说“通过平衡设计控制了顺序效应”不够，你需要说明平衡设计是如何具体实施的。
Demand characteristics occur when participants guess the aim of the study and alter their behaviour accordingly. They can be reduced by using a single-blind procedure or a cover story. Investigator effects happen when a researcher’s expectations influence the outcome; a double-blind procedure can help. In ‘suggest improvements’ questions, always link your suggestion directly to the weakness you have identified and explain how it would solve the problem.
当参与者猜到研究目的并相应地改变行为时，就产生了要求特征。可以通过单盲设计或一个掩饰性的故事来减少这一影响。研究者效应则发生在研究者的预期影响结果时；双盲设计有助于避免。在面对“提出改进建议”类题目时，永远要把你的建议直接联系到你已找出的弱点上，并解释它如何能解决该问题。
12. Applying Skills to Past Paper Scenarios | 应用：历年真题场景分析
Exam questions on experiments often present a short scenario describing a flawed investigation, then ask you to identify the IV, DV, design, one weakness, and an improvement. Read the description carefully: the IV may be implied rather than stated directly, and the design might be mixed or unclear. Practise underlining the parts of the text that indicate the design and variables before you write anything.
实验类考题通常给出一个简短的场景，描述一个存在缺陷的研究，然后要求你指出 IV、DV、设计类型、一个弱点以及一个改进建议。仔细阅读描述：IV 可能是隐含而非直接陈述的，设计类型也可能是混合或模糊的。在动笔之前，先练习划出文本中表明设计类型和变量的部分。
When asked to suggest an improvement, avoid generic answers like ‘use a larger sample’ unless you also explain how that helps (e.g., ‘a larger sample would increase the representativeness of the findings for the target population’). For an observation, consider whether covert or overt observation is more appropriate, whether categories are exhaustive and mutually exclusive, and whether inter-observer reliability has been checked. Tailored, specific suggestions earn the highest marks.
被要求提出改进建议时，避免“使用更大样本”这类笼统回答，除非你同时解释这样做的益处（如“更大样本能提高研究结果对目标人群的代表性”）。对于观察法，考虑隐蔽观察或公开观察哪个更合适、行为类别是否详尽互斥、是否检查了观察者信度。有针对性的、具体的建议才能拿到最高分。
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