Question

independent practice
mrs. davis teaches statistics. she has 2 versions of her midterm exam and she wonders if either version is more difficult than the other. she teaches approximately 160 total students in 4 sections of the class. she randomly assigns half of the students in each section to each version of the exam. mrs. davis will then see if the average scores are significantly different between each version.
what type of experimental design is this?
a stratified random design
a matched pairs design
a completely randomized design
a randomized block design

Explanation:

• Stratified random design: Involves dividing the population into subgroups (strata) and then randomly sampling from each stratum. Here, the key is not just dividing into sections (which could be seen as strata - like in stratified design), but the assignment within each section (block) to different treatments (exam versions).
• Matched pairs design: Usually has pairs of experimental units (like twins, or same - unit measured twice). This is not the case here.
• Completely randomized design: Would randomly assign all 160 students to two groups (exam versions) without considering the section structure. But here, the assignment is within sections.
• Randomized block design: Blocks are formed (the 4 sections are blocks). Within each block (section), half of the students are randomly assigned to each treatment (exam version). This fits the description of a randomized block design.

Answer:

A randomized block design