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The paper "Effect of a Nutritional Supplement on Hair Loss in Women" (Journal of Cosmetic Dermatology \([2015]: 76-82)\) describes an experiment to see if a dietary supplement consisting of Omega \(3,\) Omega \(6,\) and antioxidants could reduce hair loss in women with stage 1 hair loss. One hundred twenty women volunteered to participate in the study and were randomly assigned to either the supplement group or a control group. The women in the supplement group took the supplement for 6 months. Photos of the top of the head were taken of all the women at the beginning of the study and 6 months later at the end of the study. The two photos of each woman were evaluated by an independent expert who visually determined the change in hair density. The expert who determined the change in hair density did not know which of the women had taken the supplement. Answer the following seven questions for the described experiment. (Hint: Reviewing Examples 1.6 and 1.7 might be helpful.) 1\. What question is the experiment trying to answer? 2\. What are the experimental conditions (treatments) for this experiment? 3\. What is the response variable? 4\. What are the experimental units and how were they selected? 5\. Does the design incorporate random assignment of experimental units to the different experimental conditions? If not, are there potentially confounding variables that would make it difficult to draw conclusions based on data from the experiment? 6\. Does the experiment incorporate a control group and/ or a placebo group? If not, would the experiment be improved by including one or both of these? 7\. Does the experiment involve blinding? If not, would the experiment be improved by making it single- or double-blind?

Step by step solution

01

Question

The experiment is trying to answer the question, "Does a dietary supplement consisting of Omega 3, Omega 6, and antioxidants reduce hair loss in women with stage 1 hair loss?" 2. Experimental conditions (treatments)

02

Experimental Conditions

There are two experimental conditions for this experiment: a) The supplement group: Women in this group take the dietary supplement for 6 months. b) The control group: Women in this group do not take the dietary supplement. 3. Response variable

03

Response Variable

The response variable in this experiment is the change in hair density, determined by comparing photos of the top of the head before and after the experiment. 4. Experimental units and selection

04

Experimental Units and Selection

The experimental units in this study are the 120 women with stage 1 hair loss who volunteered to participate. They were randomly assigned to either the supplement group or the control group. 5. Random assignment of units to conditions

05

Random Assignment

Yes, the design incorporates random assignment of experimental units to the different experimental conditions. This helps to control potential confounding variables and strengthens the conclusions drawn from the experiment. 6. Control group and/or placebo group

06

Control and Placebo Groups

The experiment incorporates a control group (the women who did not take the supplement). A placebo group is not mentioned, but the experiment might be improved by including a placebo group, where participants take a non-effective, harmless pill to ensure both groups undergo similar conditions, strengthening the overall study. 7. Experiment blinding

07

Blinding

The experiment involves single blinding as the independent expert who visually determined the change in hair density did not know which women had taken the supplement. This helps to minimize bias in the evaluation of the results. Double-blinding could be implemented by also blinding the participants themselves to whether they are in the supplement or control group (or a potential placebo group). This would further help to control any biases or placebo effects.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Random Assignment

Random assignment is a critical process in experimental design that helps ensure each participant has an equal chance of being placed in either treatment group. In the study about the effects of a nutritional supplement on hair loss in women, 120 women were randomly assigned to either the supplement group or the control group. This process helps to minimize biases and confounding variables, making the results more reliable. By using random assignment:

• We avoid selection bias, ensuring that characteristics like age or baseline hair condition are evenly distributed between both groups.
• This method increases the validity of the causal conclusions drawn from the study, as any observed effects can more confidently be attributed to the supplement itself rather than other external factors.
• It simplifies data analysis by balancing unknown factors across the test and control groups.

Response Variable

The response variable is an essential part of understanding what the experiment aims to measure or what outcome is being evaluated. In this study, the response variable is the change in hair density, assessed by comparing photographs taken before and after the 6-month treatment. Why is a response variable important?

• It provides a quantifiable measure of the experiment's effects, allowing for objective evaluation and statistical analysis.
• In this case, it clearly indicates whether the nutritional supplement has an impact on hair loss reduction.
• By using photos evaluated by an independent expert, the study aims to ensure that the measurement is as unbiased and accurate as possible.

Thus, the response variable acts as the focal point for determining the success or failure of the treatment.

Control Group

A control group is a fundamental component of experimental design, serving as a benchmark against which the effects of the experimental treatment are measured. In the described experiment, the control group consists of women who did not receive the nutritional supplement. Significance of a control group:

• It allows researchers to isolate the treatment effects by comparing results between the control group and the supplement group.
• The comparison helps to compensate for external variables that might influence the results, ensuring the observed changes are due to the treatment itself.
• It also helps to highlight natural changes over time, giving a clearer picture of the treatment's efficacy.

Though a placebo group was not included in this study, its incorporation could further strengthen the findings by ensuring that any psychological effects of taking a supplement are accounted for.

Blinding

Blinding is a technique used in experiments to prevent bias by ensuring that participants and/or experimenters do not know who is receiving the treatment or placebo. In the hair loss study, blinding was used in one key way: - The independent expert who evaluated the change in hair density was blinded to whether the women had taken the supplement. This practice is known as single blinding and helps to reduce bias during result interpretation. Why blinding matters:

• It increases the objectivity of the experiment by minimizing conscious or subconscious influence during measurements or observations.
• It enhances credibility, as the results are less likely to be influenced by the expectations of either the researchers or the participants.
• In some cases, double blinding, where both participants and evaluators are unaware of group assignments, is used to further eliminate bias.

Incorporating double blinding in this study—by not informing the women whether they received the actual supplement or a non-effective placebo—could further enhance result reliability.