📚 Year 11 CAIE Psychology: Key Points for Experiments / Practical Assessment | Year 11 CAIE 心理学：实验/实践考核要点
In the CAIE IGCSE Psychology (0625) curriculum, Paper 2: Research Methods is the component that directly assesses your understanding of how psychological experiments and practical investigations are designed, conducted and evaluated. This paper is worth 50% of the total marks and requires you to apply knowledge of experimental methodology, rather than simply recalling studies. To excel, you need a solid grasp of hypotheses, variables, experimental designs, controls, sampling, ethical principles, data handling and critical evaluation skills. This article breaks down the essential points for your revision, ensuring you are fully prepared for any experiment-based question in the exam.
在CAIE IGCSE心理学（0625）课程中，Paper 2：研究方法直接考查你对心理学实验和实际调查的设计、实施和评估的理解。该试卷占总分的50%，要求你应用实验方法学的知识，而不仅仅是回忆研究。要想取得好成绩，你需要扎实掌握假设、变量、实验设计、控制、抽样、伦理原则、数据处理和批判性评估技能。本文将分解修订中的关键要点，确保你为考试中的任何基于实验的问题做好充分准备。
1. Paper 2 Assessment Overview | Paper 2 考核概述
Paper 2 accounts for 50% of the IGCSE Psychology qualification. It has a maximum of 40 marks and lasts 1 hour 15 minutes. The paper includes short-answer and extended-answer questions that assess three major skill areas: knowledge of research methods and ethical issues, data analysis and interpretation, and evaluation of studies.
Paper 2占IGCSE心理学资格评估的50%，满分为40分，考试时长1小时15分钟。试卷包含简答题和扩展题，评估三大技能领域：研究方法和伦理问题的知识、数据分析与解读、以及研究评估。
You will not carry out a real experiment during the exam; instead, you answer questions based on scenarios. Typical tasks include designing an experiment, identifying independent and dependent variables, formulating hypotheses, selecting an appropriate experimental design, discussing controls, and suggesting improvements.
考试中你并不会进行真实的实验；而是根据情景回答问题。典型任务包括设计实验、识别自变量和因变量、提出假设、选择合适的实验设计、讨论控制方法以及提出改进建议。
You may also be asked to calculate descriptive statistics (mean, median, mode, range), sketch a simple graph, or identify the most suitable graph for a given data set. Evaluation questions require you to assess the reliability, validity and ethical considerations of a study.
你还可能被要求计算描述统计量（平均数、中位数、众数、范围），绘制简图，或为给定数据集选择最合适的图表。评估题要求你评价研究的信度、效度和伦理考量。
To perform well, you must be precise with terminology and able to justify your choices. Always link your answers to the given scenario rather than giving generic definitions. Time management is crucial: allocate roughly one minute per mark.
要取得好成绩，你必须准确使用术语并能解释你的选择。始终将答案与给定的情景联系起来，而不是给出笼统的定义。时间管理至关重要：大概按照每一分分配一分钟来作答。
2. Research Aims and Hypotheses | 研究目的与假设
A research aim is a general statement of what the researcher intends to investigate, for example 'To investigate whether background noise affects memory'. An aim should be clear and focused, guiding the entire study.
研究目的是关于研究者打算调查什么的一般性陈述，例如“调查背景噪音是否影响记忆”。目的应当明确、有针对性，并指导整个研究。
From the aim, you derive a hypothesis – a precise, testable prediction about the relationship between two or more variables. In IGCSE, you will use an alternative (experimental) hypothesis and a null hypothesis.
从目的出发，你得出假设——一个关于两个或多个变量之间关系的精确、可检验的预测。在IGCSE中，你将使用备择（实验）假设和零假设。
The alternative hypothesis predicts that there will be a difference or relationship (e.g., 'Participants who complete a memory test in silence will recall more words than those who hear background music'). It can be directional (one-tailed) or non-directional (two-tailed). A directional hypothesis states the expected direction of the effect, while a non-directional hypothesis simply states there will be a difference without specifying which condition will be higher.
备择假设预测存在差异或关系（例如，“在安静环境下完成记忆测试的参与者会比听到背景音乐的参与者回忆更多单词”）。它可以是方向性（单尾）或非方向性（双尾）的。方向性假设陈述了预期的效应方向，而非方向性假设只表明存在差异，但不具体指出哪个条件会更高。
The null hypothesis states that any difference or relationship is due to chance and that no real effect exists (e.g., 'There will be no significant difference in the number of words recalled between the silent and music conditions, and any observed difference is due to chance'). Always include the phrase 'due to chance' in a null hypothesis to be fully accurate.
零假设表明任何差异或关系都是偶然的，不存在真正的效应（例如，“安静条件和音乐条件之间回忆的单词数没有显著差异，任何观察到的差异都是由于偶然”）。务必在零假设中包含“由于偶然”这个短语，以确保完全准确。
3. Variables and Operationalisation | 变量与操作化
An independent variable (IV) is the variable that the researcher manipulates or changes, and a dependent variable (DV) is the variable that is measured. For example, in an experiment on the effect of sleep on reaction time, the IV is amount of sleep and the DV is reaction time.
自变量（IV）是研究者操纵或改变的变量，因变量（DV）是被测量的变量。例如，在研究睡眠对反应时间影响的实验中，IV是睡眠时长，DV是反应时间。
Operationalisation means defining variables in a way that allows them to be measured and manipulated concretely. Instead of just 'memory', you operationalise it as 'number of words correctly recalled from a list of 20'. Clear operational definitions increase the reliability and replicability of a study.
操作化是指以允许具体测量和操纵的方式定义变量。不要只说“记忆”，而要将其操作化为“从20个单词列表中正确回忆的单词数”。清晰的操作化定义提高了研究的信度和可重复性。
Controlled variables (sometimes called constants) are factors that are kept the same across all conditions to prevent them from affecting the DV. For instance, you would control the word list, test duration, room lighting and time of day. Failing to control these can introduce confounding variables.
控制变量（有时称为常量）是在所有条件下保持相同的因素，以防止它们影响因变量。例如，你会控制单词列表、测试时长、室内照明和一天中的时间。未能控制这些变量可能引入混淆变量。
Confounding variables are uncontrolled variables that systematically change with the IV and could provide an alternative explanation for the results. For example, if participants in the music condition are tested in a warmer room than the silent condition, temperature becomes a confounding variable. Careful experimental design helps to minimise confounds.
混淆变量是随自变量系统变化且未得到控制的变量，可能为结果提供另一种解释。例如，如果音乐条件下的参与者在比安静条件更暖和的房间里接受测试，那么温度就成了混淆变量。仔细的实验设计有助于减少混淆变量。
4. Experimental Designs | 实验设计
There are three main types of experimental design that you need to know for the exam. Each has its own strengths and limitations in controlling participant variables and order effects.
考试中需要了解三种主要的实验设计类型。每种在控制参与者变量和顺序效应方面各有优缺点。
| Experimental Design | 实验设计 |
|---|---|
| Independent groups: Participants are allocated to different conditions, so each participant experiences only one level of the IV. Advantage: no order effects (practice or fatigue). Disadvantage: participant variables (e.g., intelligence, motivation) may confound results unless random allocation is used. | 独立组：参与者被分配到不同条件，每位参与者只经历一个自变量水平。优点：无顺序效应（练习或疲劳）。缺点：除非使用随机分配，否则参与者变量（如智力、动机）可能混淆结果。 |
| Repeated measures: The same participants take part in all conditions. Advantage: participant variables are perfectly controlled because the same individuals are compared. Disadvantage: order effects may occur; counterbalancing is needed to reduce this, and participants may guess the aim (demand characteristics). | 重复测量：相同的参与者参与所有条件。优点：参与者变量得到完美控制，因为比较的是相同的个体。缺点：可能出现顺序效应；需要采用平衡法来减少这一点，并且参与者可能猜测目的（需求特征）。 |
| Matched pairs: Pairs of participants are matched on a key characteristic (e.g., memory span, age) and then one member of each pair is randomly assigned to each condition. Advantage: reduces participant variables without order effects. Disadvantage: time-consuming and difficult to match perfectly on all relevant traits; some individual differences will remain. | 匹配对：参与者根据关键特征（如记忆广度、年龄）进行配对，然后每对中的一名成员被随机分配到每个条件。优点：减少参与者变量，且无顺序效应。缺点：耗时，且难以在所有相关特质上完美匹配；仍存在一些个体差异。 |
When choosing a design, consider practicality and the specific demands of the aim. Independent groups is quick but requires many participants; repeated measures uses fewer participants but may suffer from practice or fatigue effects; matched pairs is ideal when a key participant variable could distort results, but pre-testing can be time-consuming.
在选择设计时，要考虑实用性和目的的具体要求。独立组设计快捷但需要大量参与者；重复测量使用较少参与者但可能受练习或疲劳效应影响；如果关键的参与者变量可能扭曲结果，匹配对设计是理想选择，但前测可能耗时。
5. Controlling Variables | 控制变量
Standardisation is the process of keeping all procedures, instructions and environmental conditions identical for every participant. A standardised script should be read to each participant, and the same materials should be used. This reduces experimenter bias and extraneous variation.
标准化是使所有程序、指导语和环境条件对每个参与者保持一致的过程。应为每位参与者朗读标准化的讲解稿，并使用相同的材料。这减少了实验者偏差和额外变异。
Random allocation is used in independent groups designs to assign participants to conditions purely by chance (e.g., using a random number generator). This helps to evenly distribute participant variables across conditions, making groups comparable.
随机分配用于独立组设计，以纯粹随机的方式将参与者分配到各条件（例如，使用随机数生成器）。这有助于在各条件间均匀分布参与者变量，使组别具有可比性。
Counterbalancing is used in repeated measures designs. Participants are split into two groups: Group A does condition 1 then condition 2, while Group B does condition 2 then condition 1. This balances out order effects such as practice and fatigue.
平衡法用于重复测量设计。参与者被分成两组：A组先完成条件1再完成条件2，而B组先完成条件2再完成条件1。这消除了顺序效应，如练习和疲劳。
Control groups provide a baseline for comparison. In drug trials, the control group receives a placebo, allowing researchers to assess whether the IV truly causes a change. Single-blind and double-blind procedures are used to reduce demand characteristics and experimenter effects.
控制组提供了比较的基线。在药物试验中，控制组接受安慰剂，使研究者能够评估自变量是否真的造成改变。单盲和双盲程序用于减少需求特征和实验者效应。
6. Sampling Techniques | 抽样方法
A sample is a subset of the target population. The method of selecting the sample affects the representativeness of the findings and the ability to generalise. For your exam, you must know four main sampling methods.
样本是目标总体的一个子集。选择样本的方法影响研究结果的代表性和推广能力。为了备考，你必须了解四种主要的抽样方法。
Random sampling: Every member of the target population has an equal chance of being selected (e.g., drawing names from a hat). It is the most representative method and reduces sampling bias, but it can be difficult to obtain a complete list of the population.
随机抽样：目标总体中每个成员都有均等的机会被选中（例如，从帽子中抽名字）。它是最具代表性的方法，能减少抽样偏差，但获取总体的完整名单可能很困难。
Opportunity sampling: Researchers select participants who are readily available and willing (e.g., people passing by in a shopping centre). It is quick, convenient and cost-effective, but often produces a biased, unrepresentative sample.
机会抽样：研究者选择那些容易找到且愿意参与的人（例如，购物中心过往的行人）。它快速、方便且成本低，但往往产生有偏差、不具代表性的样本。
Volunteer (self-selected) sampling: Participants volunteer in response to an advertisement. It gives access to motivated participants, but the sample may be biased towards certain personality types (e.g., highly cooperative individuals), limiting generalisability.
自愿（自选）抽样：参与者响应广告自愿报名。它能获得积极主动的参与者，但样本可能偏向某些性格类型（如高度配合的个体），限制了推广性。
Stratified sampling: The researcher identifies subgroups (strata) within the population that reflect its diversity (e.g., age bands, gender), then randomly selects from each subgroup in proportion to their occurrence in the population. This yields a more representative sample, but it is complex and time-consuming.
分层抽样：研究者识别总体中反映其多样性的子群体（层）（如年龄段、性别），然后按各层在总体中的比例从各层中随机抽取。这能得到更具代表性的样本，但操作复杂且耗时。
7. Ethical Issues and Guidelines | 伦理问题与准则
Psychological research must adhere to ethical guidelines to protect participants' wellbeing and rights. In the exam, you will often be asked to identify ethical issues in a scenario and propose solutions. The core principles are based on the British Psychological Society (BPS) code of ethics.
心理学研究必须遵守伦理准则，以保护参与者的福祉和权利。考试中，你
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