Key Points for Practical Investigations in CIE IGCSE Statistics | CIE IGCSE 统计实践调查考核要点

📚 Key Points for Practical Investigations in CIE IGCSE Statistics | CIE IGCSE 统计实践调查考核要点

In the CIE IGCSE Statistics syllabus, practical investigation skills are not assessed through a separate coursework but are embedded in written examinations. You will encounter questions that describe a study, survey, or experiment and ask you to comment on the design, identify sources of bias, suggest improvements, and calculate appropriate statistics.

在 CIE IGCSE 统计学教学大纲中，实践调查技能并不通过单独的课程作业来考核，而是融入在笔试当中。你会遇到描述一项研究、调查或实验的题目，要求你评述设计、找出偏差来源、提出改进建议并计算恰当的统计量。

Mastering these evaluation skills is critical for achieving high marks. This guide covers key concepts and common pitfalls in statistical investigations.

掌握这些评估技能对于取得高分至关重要。本指南涵盖统计调查中的关键概念和常见误区。

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1. Understanding Different Types of Data | 了解不同数据类型

Data is at the heart of every investigation. It can be qualitative (non‑numerical, e.g. favourite colour) or quantitative (numerical, e.g. height). Quantitative data is either discrete (countable, like number of siblings) or continuous (measurable, like weight).

数据是每一次调查的核心。它可以是定性数据（非数值，如最喜欢的颜色）或定量数据（数值，如身高）。定量数据要么是离散型（可计数，如兄弟姐妹数量），要么是连续型（可测量，如体重）。

Knowing the data type determines which diagrams and summary statistics are appropriate. For qualitative data you would use bar charts or pie charts; for continuous data, a histogram or a cumulative frequency graph is suitable.

了解数据类型决定了哪些图表和汇总统计量是合适的。对于定性数据，可使用条形图或饼图；对于连续数据，直方图或累积频数图是合适的。

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2. Primary vs Secondary Data | 一手数据与二手数据

Primary data is collected by the investigator specifically for the purpose of the study, through experiments, surveys, or observations. Secondary data is already available, having been collected by someone else, such as government statistics or previous research.

一手数据是研究者为特定研究目的而亲自通过实验、调查或观察收集的数据。二手数据是已有的、由他人收集的数据，如政府统计资料或先前的研究。

Primary data is often more reliable for your specific research question but can be time‑consuming to gather. Secondary data is cheaper and quicker to obtain but may not perfectly match your needs or may contain errors.

一手数据通常对你的特定研究问题更可靠，但收集起来费时。二手数据获取成本更低、更快，但可能不完全匹配你的需求或含有错误。

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3. Sampling Techniques | 抽样方法

When you cannot survey the whole population, you select a sample. The sample must be representative to avoid bias.

当无法调查整个总体时，你需要选取一个样本。样本必须具有代表性才能避免偏差。

Simple random sampling: every member has an equal chance of selection, usually using random numbers.

简单随机抽样：每个成员都有均等的机会被选中，通常使用随机数。

Stratified sampling: the population is divided into groups (strata) based on a characteristic, and a random sample is taken from each stratum in proportion to the population size. This ensures all groups are fairly represented.

分层抽样：将总体根据某个特征分成若干层，再从每一层中按总体比例随机抽取样本。这确保所有群体都得到公平代表。

Systematic sampling: you choose a starting point randomly and then select every k‑th individual. This is easy to implement but can introduce bias if there is an underlying pattern.

系统抽样：随机选择一个起点，然后每隔 k 个个体选取一个。这种方法易于实施，但如果存在潜在规律就可能引入偏差。

Quota sampling: the interviewer is given quotas for different groups (e.g. 50 males, 50 females) but selects individuals non‑randomly. It is cheap but not random.

配额抽样：采访者被给予不同群体的配额（例如 50 名男性、50 名女性），但以非随机方式选取个体。成本低但不随机。

Cluster sampling: the population is divided into clusters (e.g. schools), some clusters are chosen randomly, and all members of selected clusters are surveyed. This is useful for large populations but can be less precise.

整群抽样：将总体分成若干群（如学校），随机选择一些群，然后调查选中群的所有成员。对于大规模总体很有用，但精确度较低。

Questions may ask you to identify the sampling method used or suggest the most appropriate method for a given scenario. Always consider practicality, cost, and the need for a representative sample.

题目可能会要求你识别所用的抽样方法，或为给定情景建议最合适的方法。始终要考虑可行性、成本以及样本代表性的需要。

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4. Designing a Questionnaire | 设计调查问卷

A well‑designed questionnaire is essential for collecting reliable data. Questions must be clear, unambiguous, and easy to answer.

精心设计的问卷对于收集可靠数据至关重要。问题必须清晰、无歧义且易于回答。

Use closed questions (with a limited set of response options) for quantitative analysis, and open questions for richer qualitative insight. Avoid leading questions that push respondents towards a particular answer, e.g. ‘Don’t you agree that homework is beneficial?’

使用封闭式问题（有有限选项）以便定量分析，使用开放式问题以获取更丰富的定性见解。避免引导性问题，即把受访者推向某个特定答案，例如“你难道不认为家庭作业是有益的吗？”

Response categories should be exhaustive and mutually exclusive. If you ask for age bands, make sure every possible age fits into exactly one band.

回答选项应穷尽且互斥。如果你询问年龄段，确保每个可能的年龄恰好属于一个区间。

Pilot the questionnaire on a small group to

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