The researcher attempts to control and/or manipulate the variables. 研究者尝试控制和/或操纵变量。
Ex Post Facto 事后设计
The researcher has no control over the variables; can only report what happened. 研究者对变量没有控制,只能报告已经发生的事。
5.6Purpose 研究目的
Descriptive 描述性:answer who, what, when, how much; discovery of associations among variables; cross-tabulations and bivariate correlations. 回答谁、什么、何时、多少;发现变量间的关联(交叉表、双变量相关)。
Causal 因果性:how one variable affects another; A produces / forces B. 一个变量如何影响另一个;A 产生/迫使 B。
Predictive 预测性:attempt to estimate what will happen in the future. 尝试估计未来会发生什么。
5.7Topical Scope 主题范围
Statistical Studies 统计研究
Capture a population's characteristics by making inferences from a sample's characteristics. 通过样本特征推断总体特征。
Case Studies 案例研究
More emphasis on a full contextual analysis of fewer events or conditions and their interrelations. 更强调对较少事件/情境的完整情境分析及其相互关系。
5.8Time Dimension 时间维度
Cross-sectional 横截面
Carried out once — a snapshot of one point in time. 只进行一次,是一个时间点的快照。
Longitudinal 纵向
Repeated over an extended period. 在较长一段时间内重复进行。
5.9Exploratory Techniques (4) 探索性技术(四种)
1) Qualitative techniques / Experience surveys 定性技术/经验调查:in-depth or elite interviews, observation (inductive — generate new ideas); interview/observe a variety of people, not only key persons. Experience surveys ask: what is being done, what was tried, what changed, barriers, costs, priorities. 深度/精英访谈与观察(归纳式,产生新想法);访谈、观察各类人,不只关键人物。经验调查问:在做什么、试过什么、变了什么、障碍、成本、优先级。
2) Secondary data analysis 二手数据分析:prior studies, documents — essentially a literature review. 既有研究与文档——本质上就是文献综述。
3) Focus groups 焦点小组:composition better if homogeneous; if participants are heterogeneous, consider splitting; quality depends crucially on the moderator's ability to trigger discussion. 成员同质更好;异质时考虑分组;质量关键取决于主持人引发讨论的能力。
4) Two-stage designs 两阶段设计:stage 1 explore to find a feasible research problem; stage 2 explore to find appropriate designs (or further exploration/explanation). 第一阶段探索可行的研究问题;第二阶段探索合适的研究设计(或进一步探索/解释)。
5.10Causation 因果关系
Essential element: A produces B / A forces B to occur. 核心要素:A 产生 B / A 迫使 B 发生。Three conditions 三个条件:
Covariation 共变:if A occurs, B also occurs; if A is absent, B is absent; less A = less B. A 出现 B 也出现;A 不在 B 也不在;A 减少 B 也减少。
Time order 时间顺序:A must occur before B. A 必须发生在 B 之前。
Exclusiveness 排他性:no other possible causes for B. B 没有其他可能的成因。
5.11Confounding Variable / Confounder 混杂变量
A type of extraneous variable related to both the independent and the dependent variables. 一种与自变量和因变量都相关的外来变量。Two conditions 两个条件:
1) Must be correlated with the independent variable (may or may not be causal). 必须与自变量相关(可以是因果关系,也可以不是)。
2) Must be causally related to the dependent variable. 必须与因变量有因果关系。
Classic example 经典例子:temperature 气温 sits behind both ice-cream sales and drowning. 气温同时在冰淇淋销量和溺水事件背后。
Depends on 取决于:the research problem (at what level do we look for answers) · at what level we need/measure information · at what level we want to implement the answers. 研究问题(在哪一层级寻找答案)、在哪一层级需要/测量信息、在哪一层级落实答案。
6.2Core Concepts 核心概念
Population 总体 · Population Element 总体元素 · Sample 样本 · Census 普查(special case: the whole population is the sample 特例:整个总体即为样本)
6.3Why Sample Instead of Census? 为什么抽样而不普查
Lower costs + faster 成本更低、速度更快。
Greater accuracy 准确性可能更高 — trade-off: asking everybody vs obtaining better/more data from a representative sub-group. 权衡:问所有人,还是从有代表性的子集获得更好/更多的数据。
Availability of population elements 总体元素是否可获得。
6.4What Is a Good Sample? 什么是好样本
Accuracy 准确性 = absence of systematic variance (bias). 没有系统性偏差。
Precise estimate 精确估计 = sampling error should be random error; a sample will by chance differ from the population (no way to avoid it), and this decreases with sample size. 抽样误差应只是随机误差;样本因随机机会与总体不同在所难免,且随样本量增大而减小。
6.5Six Steps in the Sampling Process 抽样流程六步
1) What is the relevant population? 相关的总体是什么?
2) What are the parameters of interest? 关注的参数是什么?
3) What is the sampling frame? 抽样框是什么?
4) What is the type of sample? 样本类型是什么?
5) What size sample is needed? 需要多大的样本?
6) How much will it cost? 成本多少?
6.6Key Concepts for Probability Sampling & Sample Size 概率抽样与样本量的关键概念
Standard Error 标准误 · Confidence Interval 置信区间 · Central Limit Theorem 中心极限定理
6.7What Determines Sample Size? 什么决定样本量
Greater dispersion / variance within population → larger sample needed. 总体内离散/方差越大 → 样本要越大。