📚 Year 8 Edexcel Psychology: Formulae & Key Principles Quick Reference Guide | Year 8 爱德思心理学：公式与定理速查手册
This quick reference guide brings together the essential formulae and key psychological principles you will encounter in Year 8 Edexcel Psychology. Whether you are analysing data from a class experiment or revising core theories, having these tools at your fingertips will sharpen your understanding and boost your exam confidence. Each entry is presented with a concise explanation and a worked example where appropriate, followed by a paired Chinese translation to support bilingual learners.
本速查手册汇集了 Year 8 爱德思心理学中会遇到的核心公式和关键心理学定理。无论你是在分析课堂实验的数据，还是在复习核心理论，随时查阅这些工具都能加深你的理解并提升考试信心。每个条目都附有简洁的解释和适当的示例，并配有对应的中文翻译，以辅助双语学习。
1. Measures of Central Tendency | 集中趋势的测量
Psychologists summarise large sets of data by finding a typical or central value. The three most common measures of central tendency are the mean, median, and mode. Each has its own formula and is useful in different situations.
心理学家通过寻找典型值或中心值来概括大量数据。三种最常见的集中趋势测量指标是 平均值、中位数 和 众数。每种都有各自的公式，并在不同情况下各有用途。
The mean is found by adding all scores together and dividing by the total number of scores. It is the most sensitive measure because it uses every data point, but it can be dragged up or down by extreme outliers.
平均值 是将所有分数相加后除以分数的总数。它是最灵敏的测量指标，因为它使用了每一个数据点，但极易受到极端异常值的影响而偏高或偏低。
Mean = Σx ÷ n
式中 Σx 为所有分数的总和，n 为分数的个数。
The median is the middle score when all values are arranged in order from smallest to largest. If there is an even number of scores, the median is the mean of the two middle values. The median is not affected by outliers, making it ideal for skewed data.
中位数 是把所有数值按从小到大的顺序排列后位于中间的那个分数。如果有偶数个分数，中位数就是中间两个分数的平均值。中位数不受异常值影响，因此非常适合偏态数据。
The mode is simply the most frequently occurring value in a data set. A set may have one mode, more than one mode (bimodal/multimodal), or no mode at all. It is the only measure that can be used with nominal (category) data.
众数 就是数据集中出现频率最高的数值。一组数据可能有一个众数、多个众数（双峰/多峰），或者根本没有众数。它是唯一可用于称名（类别）数据的测量指标。
2. Measures of Dispersion: The Range | 离散趋势：极差
Central tendency alone does not tell us how spread out the scores are. Dispersion describes the variability within a data set. The simplest measure of dispersion is the range.
仅靠集中趋势并不能告诉我们分数的分散程度。离散度 描述了数据集内部的变异性。最简单的离散测量指标是 极差。
The range is calculated by subtracting the smallest value from the largest value. A small range indicates that scores are closely bunched together, while a large range shows wide variation. However, the range only considers the two extreme values and ignores the distribution of the rest of the data.
极差的计算方法是用最大值减去最小值。极差小表明分数紧密聚集在一起，极差大则显示变异很大。但极差只考虑了两个极端值，而忽略了其余数据的分布情况。
Range = Highest score – Lowest score
例如：数据集 5, 8, 9, 12, 17 的极差为 17 – 5 = 12。
3. Calculating Percentage Change | 计算百分比变化
When comparing before-and-after measurements in psychology, researchers often express the difference as a percentage change. This formula is particularly useful for evaluating improvements in memory experiments or changes in behaviour following an intervention.
在心理学中比较前后测量值时，研究者常用 百分比变化 来表示差异。这个公式在评估记忆实验中的进步或干预后的行为变化时尤其有用。
Percentage Change = (New value – Original value) ÷ Original value × 100%
If a participant’s recall score rises from 12 to 15, the percentage increase is (15 – 12) ÷ 12 × 100% = 25%. A negative result indicates a percentage decrease.
如果一位参与者的回忆分数从 12 提高到 15，那么百分比增长为 (15 – 12) ÷ 12 × 100% = 25%。结果为负则表示百分比下降。
4. Miller’s Magic Number: 7 ± 2 | 米勒的神奇数字：7±2
One of the most famous ‘laws’ in cognitive psychology comes from George Miller (1956), who proposed that the capacity of short-term memory is limited to about seven items, plus or minus two. This means most people can hold between five and nine chunks of information in mind at once.
认知心理学中最著名的“定律”之一来自乔治·米勒（1956），他提出 短时记忆 的容量大约为 7±2 个项目。这意味着大多数人一次能在脑海中保持 5 到 9 个信息组块。
STM capacity ≈ 7 ± 2 chunks
Chunking can expand functional memory: remembering the letter sequence FBICIAUK is easier when chunked as FBI, CIA, UK. This principle underpins many revision techniques and explains why phone numbers are broken into small groups.
组块化可以扩展功能性记忆：记住字母序列 FBICIAUK 时，如果分成 FBI、CIA、UK 三个组块就更容易。这一原理是许多复习技巧的基础，也解释了为什么电话号码被分成小组。
5. The Ebbinghaus Forgetting Curve | 艾宾浩斯遗忘曲线
Hermann Ebbinghaus (1885) discovered that memory for newly learned information decays rapidly at first and then levels off. The forgetting curve illustrates this exponential loss and highlights the importance of timely revision.
赫尔曼·艾宾浩斯（1885）发现，新学信息的记忆起初遗忘得很快，随后遗忘速度逐渐放缓。遗忘曲线 展示了这种指数式损失，并凸显了及时复习的重要性。
Key findings: roughly 50% of meaningless material is forgotten within an hour, and about 70% after 24 hours. However, meaningful material and regular rehearsal can flatten the curve, making recall much more durable.
关键发现：大约 50% 的无意义材料在一小时内被遗忘，24 小时后约遗忘 70%。但有意义的材料和定期复述可以使曲线变得平缓，使回忆更加持久。
Retention (%) decreases most steeply immediately after learning.
遗忘曲线在考试复习中是最重要的实验发现之一，它提醒我们间隔复习优于考前突击。
6. The Yerkes-Dodson Law | 耶克斯-多德森定律
The Yerkes-Dodson Law states that performance increases with physiological or mental arousal, but only up to an optimal point. Beyond that optimum, further arousal leads to a decline in performance. This relationship is often drawn as an inverted U-shaped curve.
耶克斯-多德森定律指出，表现会随着生理或心理唤醒水平的提高而提高，但只到达一个最优点为止。超过最优点后，进一步的唤醒会导致表现下降。这种关系通常被绘制成倒U形曲线。
For simple or well-practiced tasks, the optimal level of arousal is higher; for complex or new tasks, the optimum is lower. An athlete needs high arousal before a sprint, but a snooker player requires calm concentration.
对于简单或熟练的任务，最佳唤醒水平较高；对于复杂或新任务，最佳唤醒水平较低。短跑运动员在赛前需要高唤醒，而斯诺克选手则需要平静的专注。
Performance = f(arousal), optimal at moderate arousal
这一“定律”在体育心理学、考试焦虑管理和广告设计中都有广泛的应用。
7. Conformity: Asch’s Key Findings | 从众：阿施的关键发现
Solomon Asch (1951) demonstrated that people often conform to the majority even when the majority is clearly wrong. In his line-judgement experiments, about 75% of participants conformed at least once, and the overall conformity rate was approximately 37% across all critical trials.
所罗门·阿施（1951）证明，即使多数人的判断明显错误，人们也常常会从众。在他的线段判断实验中，大约 75% 的参与者至少从众过一次，所有关键试次的总体从众率约为 37%。
Asch identified key variables affecting conformity: group size (conformity increases up to about 4–5 confederates), unanimity (a single dissenter sharply reduces conformity), and task difficulty (harder tasks increase conformity because we look to others for information). These findings form a ‘principle’ of social influence.
阿施确定了影响从众的关键变量：群体规模（从众率在约4–5名同谋者时达到最高）、一致性（哪怕只有一个异议者也会急降从众率）和任务难度（任务越难，从众越高，因为我们会参考他人信息）。这些发现构成了社会影响的一个“原理”。
8. Deindividuation and Zimbardo’s Stanford Prison Experiment | 去个性化与津巴多的斯坦福监狱实验
Deindividuation refers to a psychological state in which an individual loses their sense of personal identity and self-awareness, often when immersed in a crowd or wearing a uniform. This can lead to disinhibited and antisocial behaviour. Zimbardo’s 1971 Stanford Prison Experiment demonstrated how quickly anonymous roles could erode personal norms.
去个性化指个体在融入人群或穿着制服时失去个人认同感和自我意识的一种心理状态。这可能导致行为失控和反社会行为。津巴多1971年的斯坦福监狱实验证明了匿名角色能多快地侵蚀个人规范。
The guards, given uniforms and mirrored sunglasses, became increasingly abusive, while the prisoners showed signs of extreme stress. The study had to be stopped after only six days. The ‘law’ here is that anonymity + group setting can overpower individual conscience.
被给予制服和反光太阳镜的“看守”变得越来越残暴，而“囚犯”则表现出极度紧张的迹象。实验仅仅六天后就被迫终止。这里的“定律”是：匿名性 + 群体环境可以压倒个人良知。
9. Operationalisation of Variables | 变量的操作性定义
In any psychological investigation, it is essential to turn abstract ideas into measurable factors. Operationalisation means clearly defining how the independent variable (IV) and the dependent variable (DV) will be manipulated or measured. Without a precise operational definition, a study cannot be replicated.
在任何心理学研究中，把抽象概念转化为可测量的因素至关重要。操作性定义 指的是明确说明如何操纵 自变量 (IV) 和如何测量 因变量 (DV)。没有精确的操作性定义，研究就无法被重复。
IV (manipulated) → DV (measured)
For example, the hypothesis ‘caffeine improves memory’ becomes operationalised as ‘Participants given 200 mg of caffeine (IV) will recall more words from a 20-word list (DV) than participants given a placebo’.
例如，“咖啡因改善记忆”这一假设就可以被操作化为：“摄入200毫克咖啡因（IV）的参与者比服用安慰剂的参与者能从包含20个单词的列表中回忆出更多的单词（DV）”。
10. Ethical Principles in Psychological Research | 心理学研究的伦理原则
Every Year 8 psychology student must learn the core ethical guidelines that protect participants. These principles are not mathematical formulae but are absolute ‘rules’ that govern all legitimate research. They stem from the British Psychological Society (BPS) Code of Ethics.
每个 Year 8 的心理学学生都必须学习保护参与者的核心伦理准则。这些原则并非数学公式，而是支配所有合法研究的绝对“规则”。它们源自英国心理学会（BPS）的伦理规范。
- Informed consent: Participants must know the aim and agree to take part. 知情同意：参与者必须知晓研究目的并同意参与。
- Right to withdraw: Participants can leave at any time without penalty. 退出权：参与者可随时退出而不受惩罚。
- Confidentiality: Personal data must be kept private. 保密性：个人数据必须保密。
- Protection from harm: No physical or psychological harm should occur. 免受伤害：不应造成任何身体或心理伤害。
- Deception: Should be avoided; if used, a full debrief is required. 欺骗：应避免使用欺骗；若使用，则必须进行充分的解释说明。
These ethical ‘formulae’ ensure that the pursuit of knowledge never overrides human dignity.
这些伦理“公式”确保了追求知识永远不会凌驾于人的尊严之上。
11. Research Design and Participant Allocation | 研究设计与参与者分配
Choosing the right experimental design is vital for valid results. The three main designs are independent groups (different participants in each condition), repeated measures (same participants in all conditions), and matched pairs (participants are paired on key traits and split).
选择合适的实验设计对获得有效结果至关重要。三种主要设计是 独立组设计（不同参与者分别进入不同条件）、重复测量设计（相同参与者完成所有条件）和 配对组设计（参与者在关键特质上匹配后分开）。
A simple allocation formula for independent groups is to randomly divide the participant list. For matched pairs, you pre-test and rank participants, then assign rank 1 and 2 to different conditions, rank 3 and 4 to different conditions, and so on.
独立组设计的一种简单分配“公式”是 随机划分参与者名单。对于配对组设计，你需要先进行预测试并对参与者排序，然后把排序第1和第2的分配到不同条件，第3和第4也如此，依此类推。
Random allocation minimises participant variables.
平衡参与者变量的最好方法就是随机分配或配对，从而增强内部效度。
12. Internal and External Validity | 内部效度与外部效度
Internal validity asks whether the study truly measures what it intends to measure, free from confounding variables. External validity concerns whether the findings can be generalised beyond the specific study settings, to other people, places, and times.
内部效度 问的是：研究是否真的测量了它想要测量的东西，并且没有混淆变量的干扰。外部效度 则关心研究结果能否推广到特定的研究情境之外，推广到其他人群、地点和时间。
Threats to internal validity include demand characteristics, investigator effects, and poor operationalisation. Threats to external validity include a narrow sample (e.g., only Year 8 students) and artificial laboratory settings that lack mundane realism.
内部效度的威胁包括需求特征、研究者效应以及操作性定义不充分。外部效度的威胁包括样本狭窄（例如只有 Year 8 学生）和缺乏日常生活真实性的实验室环境。
The ultimate goal is a study high in both types of validity, though in practice researchers often must strike a balance. A highly controlled lab experiment may have strong internal validity but weaker external validity.
最终目标是研究兼具高内部效度与高外部效度，尽管实践中研究者常常需要权衡取舍。一个高度受控的实验室实验可能内部效度很强，但外部效度较弱。
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