Question at position 5 This study is not well designed because the sample may not have been randomly selected.This study is not well designed because there is not enough replication with only 50 customers.This study is not well designed because there is no replication Each customer tasted the formulas only once.This study is not well designed because formulas A and B are not compared with the original formula.This study is not well designed because each customer should taste the two new formulas in order

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Question at position 5 This study is not well designed because the sample may not have been randomly selected.This study is not well designed because there is not enough replication with only 50 customers.This study is not well designed because there is no replication Each customer tasted the formulas only once.This study is not well designed because formulas A and B are not compared with the original formula.This study is not well designed because each customer should taste the two new formulas in order

BlackTom AI · Accepted Answer

First, let's restate the scenario and list all the potential issues mentioned for clarity. The question describes a study where 50 customers taste both formula A and formula B in a randomly assigned order to determine which one they prefer over the original nacho-flavored corn chip. The question then offers five statements about why the study design is not well designed.

Option A: 'This study is not well designed because the sample may not have been randomly selected.' This raises a concern about random sampling of participants. While random selection is important for generalizability to a population, the problem description emphasizes the internal design aspects (randomized tasting order, replication, comparisons), not how the sample was drawn. The statement points to external validity rather than internal validity, so it may be less central to the core design flaw described.

Option B: 'This study is not well designed because there is not enough replication with only 50 customers.' Replication refers to having enough experimental units to estimate variability. Fifty participants could be sufficient depending on the effect size and design, but the statement alone is vague. The key replication issue would be whether each condition is tested with multiple customers and whether there is enough within-subject replication to assess variability across individuals.

Option C: 'This study is not well designed because there is no replication Each customer tasted the formulas only once.' Here, the lack of replication is more explicit: each customer tastes the formulas only once, meaning we cannot assess within-subject variability across repeated tastes or guard against idiosyncratic preferences. This is a meaningful flaw because repeated measures or multiple tastings per condition improve reliability.

Option D: 'This study is not well designed because formulas A and B are not compared with the original formula.' This choice targets the need to compare new formulas A and B against the original formula as a baseline. If the original is not included in the comparison, it may hinder understanding of whether A or B offer improvement over the original product, which could be important depending on the research question. However, the primary design concern in a taste test focusing on preference between A and B versus the original is about within-subject comparisons between the new formulas and the baseline.

Option E: 'This study is not well designed because each customer should taste the two new formulas in order' This suggests a specific sequencing issue—order effects—and implies that tasting order might bias preferences. In a properly randomized order, this should be mitigated, and the problem description already mentions a randomly assigned order, so this particular flaw is addressed in the design.

Now evaluating each option against the study design described: the crucial flaw highlighted in the given correct answer is that A and B are not compared with the original formula. If the aim is to determine whether customers prefer A or B over the original, it is essential to include a direct comparison with the original formulation. Without that direct comparison, conclusions about whether A or B are improvements relative to the original cannot be drawn with confidence. The presented study design includes random order and within-subject tasting of A and B, but it omits a direct comparison to the original product, which weakens the interpretability of any preference results.

How each option stacks up:
- Option A discusses sample randomness; while random sampling affects external validity, the immediate design flaw of not including the original as a comparator is more central to internal validity in this context. Therefore A is not the best critique of the design given the setup.
- Option B mentions replication with only 50 customers. Depending on variability and effect sizes, 50 may or may not be enough, but the question’s strongest explicit design flaw is the absence of a baseline comparison, not simply limited replication.
- Option C points to no replication because each customer tasted the formulas only once. This is a valid and clear design flaw: lack of replication within subjects. However, the stem specifically asks for a flaw among the provided options, and the identified correct option emphasizes the missing baseline comparison rather than the single tasting issue.
- Option D claims formulas A and B are not compared with the original formula. This directly addresses the comparison baseline and is the most critical design limitation if the goal is to see improvements against the original product. It undermines the interpretability of preference results.
- Option E argues about tasting order, but the description states that order is randomly assigned, which should mitigate order effects. Hence E is not the core problem here.

In summary, while several issues could be argued, the strongest and most explicit design flaw given the stated aim is that A and B are not compared with the original formula, making this the correct critique among the options.

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