Selecting a Design · 选择实验设计
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| completely randomized design/kəmˈpliːtli ˈrændəmaɪzd dɪˈzaɪn/ | 完全随机设计 | wán quán suí jī shè jì |
| blocking/ˈblɒkɪŋ/ | 区组化 | qū zǔ huà |
| matched-pairs design/mætʃt peəz dɪˈzaɪn/ | 配对设计 | pèi duì shè jì |
| randomized block design/ˈrændəmaɪzd blɒk dɪˈzaɪn/ | 随机区组设计 | suí jī qū zǔ shè jì |
The completely randomized design
- The simplest design: a completely randomized design 完全随机设计.
- All experimental units are assigned to treatments purely by chance.
- No grouping first — just randomize everyone into the treatment groups.
- It relies on randomization alone to balance out differences.
完全随机设计
- 最简单的设计：完全随机设计。
- 所有实验单位都纯凭机会被分配到各处理。
- 不先分组——只是把每个人随机分进各处理组。
- 它仅依靠随机化来平衡差异。
Blocking cuts variability
- Sometimes units differ in a known way that affects the response (e.g. age, sex).
- Blocking 区组化 groups similar units into blocks, then randomizes within each block.
- This removes that known source of variation from the comparison.
- "Block what you can, randomize what you can't."
区组化减少变异
- 有时单位在一个已知的、会影响响应的方面不同（如年龄、性别）。
- 区组化把相似的单位分成区组，然后在每个区组内随机分配。
- 这从比较中移除了那个已知的变异来源。
- “能区组的就区组，不能的就随机化。”
Block and matched-pairs designs
- A randomized block design 随机区组设计: form blocks of similar units, randomize treatments inside each.
- A matched-pairs design 配对设计: the special case of blocks of size $2$.
- Match two similar units (or use the same unit twice), randomize which gets which treatment.
- Comparing within a matched pair cancels the differences between individuals.
区组设计与配对设计
- **随机区组设计：**把相似单位组成区组，在每个区组内随机分配处理。
- **配对设计：**区组大小为 $2$ 的特例。
- 匹配两个相似的单位（或把同一个单位用两次），随机决定谁接受哪种处理。
- 在一个配对内比较，抵消了个体之间的差异。
Choosing a design
- Pick the design that controls the biggest known source of variability.
- If a variable (age, baseline skill) clearly affects the response → block on it.
- If no strong nuisance variable stands out → a completely randomized design is fine.
- The goal is a fair comparison where only the treatment differs.
选择一种设计
- 选择能控制最大的已知变异来源的设计。
- 如果某个变量（年龄、基础水平）明显影响响应 → 就对它区组。
- 如果没有突出的强干扰变量 → 完全随机设计就够了。
- 目标是一次公平的比较，其中只有处理不同。
Blocking is not the same as stratifying. Same idea (group similar units), different setting: stratified sampling is about choosing a representative sample; blocking is about designing an experiment to reduce variability. Also, don't block on a variable that has nothing to do with the response — you only block on a known nuisance variable.
区组化和分层不是一回事。思想相同（把相似单位分组），场景不同：分层抽样是关于选取一个有代表性的样本；区组化是关于设计一个实验以减少变异。此外，不要对一个与响应无关的变量区组——你只对已知的干扰变量区组。
Testing a workout plan on people of very different fitness.
- Fitness strongly affects the response → block by fitness level.
- Randomized block design: within each fitness block, randomly assign plan A or B.
- Matched pairs: pair each person with a similar-fitness partner; randomize who gets A.
在体能差异很大的人群上测试一套健身计划。
- 体能强烈影响响应 → 按体能水平区组。
- **随机区组设计：**在每个体能区组内，随机分配计划 A 或 B。
- **配对：**把每个人与一个体能相近的搭档配对；随机决定谁接受 A。
A completely randomized design assigns all units to treatments by chance. Blocking groups similar units to remove a known source of variability, giving a randomized block design (or a matched-pairs design when blocks have size $2$). Choose the design that controls the largest known nuisance variable.
完全随机设计把所有单位凭机会分配到各处理。区组化把相似单位分组以移除一个已知的变异来源，得到随机区组设计（当区组大小为 $2$ 时即配对设计）。选择能控制最大已知干扰变量的设计。
Units grouped into blocks · 把单位分成区组
Blocking groups similar units before randomizing within each. · 区组化在每组内随机化之前，先把相似单位分组。
A matched-pairs design is a special case of a randomized block design with blocks of size... · 配对设计是区组大小为……的随机区组设计的特例。
Matched pairs = blocks of size 2. · 配对 = 大小为 2 的区组。
Blocking groups similar experimental units to remove a known source of variability. · 区组化把相似的实验单位分组，以移除一个已知的变异来源。
That's exactly the purpose of blocking. · 这正是区组化的目的。
Fitness strongly affects the response. The best design is to... · 体能强烈影响响应。最佳设计是……
Block on the known nuisance variable (fitness). · 对已知的干扰变量（体能）进行区组。
The simplest design, assigning all units to treatments purely by chance, is a completely ___ design. · 把所有单位纯凭机会分配到各处理的最简单设计，是完全 ___ 设计（填英文一词）。
A completely randomized design uses randomization alone. · 完全随机设计仅依靠随机化。
Blocking (in experiments) is most like which sampling method? · （实验中的）区组化最像哪种抽样方法？
Both group similar units — blocking (design) parallels stratifying (sampling). · 两者都把相似单位分组——区组（设计）对应分层（抽样）。