IGCSE CCEA Psychology: Formula & Key Laws Quick-Reference Handbook | IGCSE CCEA 心理学：公式定理速查手册

📚 IGCSE CCEA Psychology: Formula & Key Laws Quick-Reference Handbook | IGCSE CCEA 心理学：公式定理速查手册

This quick-reference handbook brings together the core statistical formulae and key psychological laws tested in CCEA IGCSE Psychology. It is designed for fast revision before end-of-topic tests and final examinations.

本速查手册汇总了 CCEA IGCSE 心理学中考查的核心统计公式与重要心理学定律，适合在单元测验和期末考试前快速复习。

1. Descriptive Statistics: Mean, Median and Mode | 描述统计：均值、中位数与众数

In CCEA IGCSE Psychology, raw data must be summarised before interpretation. Descriptive statistics condense large data sets into meaningful averages and measures of spread.

在 CCEA IGCSE 心理学中，原始数据在解释前必须先进行概括。描述统计将大量数据压缩为有意义的平均数与离散量数。

Mean = Σx ÷ N

The mean is the arithmetic average, found by adding every score and dividing by the number of participants. It is sensitive to extreme values, so an outlier can pull the mean away from the centre.

均值是算术平均数，计算方法是把所有分数相加后除以被试人数。它对极端值敏感，因此一个异常值可能会把均值拉离中心。

The median is the middle score when data are ordered from lowest to highest. The mode is the most frequently occurring score. In a skewed distribution, the median is often a better measure of central tendency than the mean.

中位数是按从低到高排序后位于中间的分数。众数是出现频率最高的分数。在偏态分布中，中位数通常比均值更适合作为集中趋势量数。

2. Measures of Spread: Range and Standard Deviation | 离散量数：极差与标准差

Measures of spread show how much scores vary. The simplest measure is the range, which is the difference between the highest and lowest values.

离散量数反映分数的变异程度。最简单的量数是极差，即最大值与最小值之差。

Range = Highest value − Lowest value

The range is quick to calculate but only uses two scores. It can be inflated by a single extreme value.

极差计算快捷，但只使用了两个分数，单个极端值就可能使其增大。

Standard deviation is a more sensitive measure. It estimates the average distance of each score from the mean. A larger standard deviation means greater variability in results; a smaller standard deviation means scores are clustered closely around the mean.

标准差是更灵敏的量数，估计每个分数与均值的平均距离。标准差越大，结果的变异性越大；标准差越小，分数越紧密地聚集在均值附近。

3. Percentage Change, Ratios and Fractions | 百分比变化、比率与分数

Researchers often compare conditions using percentage change. This shows the size of an increase or decrease relative to the original value.

研究者常用百分比变化来比较条件，显示相对于原始值的增减幅度。

Percentage change = (New value − Original value) ÷ Original value × 100

Percentage change is useful when baseline scores differ between groups. A positive result indicates an increase; a negative result indicates a decrease.

当各组基线分数不同时，百分比变化很有用。结果为正表示增加；结果为负表示减少。

Ratios and fractions also summarise data. For example, in a study of conformity, 9 out of 12 participants conforming can be expressed as 9:12, 3:4, or 75%.

比率和分数也可用于概括数据。例如，在一项从众研究中，12 名被试中有 9 名从众，可表示为 9:12、3:4 或 75%。

4. Correlation and Correlation Coefficients | 相关与相关系数

A correlation measures the strength and direction of a relationship between two co-variables. Correlation does not imply causation; a third variable

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