Question

About \(60 \%\) of a child's growth hormone is secreted during sleep, so it is believed that a lack of sleep in children might stunt growth. \(^{63}\) (a) What is the explanatory variable and what is the response variable in this association? (b) Describe a randomized comparative experiment to test this association. (c) Explain why it is difficult (and unethical) to get objective verification of this possible causal relationship.

Short answer

The explanatory variable is 'sleep' and the response variable is 'growth'. A comparative experiment could involve splitting a number of similar subjects into control and experimental groups, with the latter having their sleep limited, and observing growth over time. However, intentionally depriving children of sleep poses ethical issues, making objective verification difficult.

Step-by-step solution

Identify Explanatory & Response Variables

The explanatory variable is the variable that is manipulated to check its effects on the other. Here, it's 'sleep'. The response variable is the one that the experiment assesses to see if it has changed. Here, it's 'growth'.

Design a Comparative Experiment

This would involve selecting a sample of similar subjects — for example, same-age, same-gender children. Group them randomly into two: a control group that maintains a normal sleep cycle and an experimental group that has their sleep limited. Observe and measure growth over a significant period of time.

Identifying Ethical Boundaries

Deprivation of sleep in children for the purpose of testing could lead to negative side effects and this could be considered harm which is unethical in an experiment. Objective verification of this relationship will be difficult as it can involve potentially harmful interventions with a child's sleep.

Key concepts

Explanatory Variable

In research and experimentation, an explanatory variable is one that is manipulated by the researcher to explore its effects on another variable. The aim is to uncover if and how this independent variable influences the dependent variable, which is typically the outcome of interest. For instance, in studying the connection between sleep and growth in children, sleep would be the explanatory variable. This is because it is the aspect that scientists would alter or regulate to observe whether changes in sleep patterns lead to variance in growth rates.

Understanding the explanatory variable is crucial because it sets the stage for a cause-and-effect analysis within the experiment. When designing experiments, researchers must ensure they can control or at least account for the explanatory variable to establish a clear linkage to the outcomes they measure. Moreover, isolating this variable helps to distinguish between correlation and causation, ensuring that other factors do not confound the observed effect.

Response Variable

The response variable, also known as the dependent variable, is the one that is measured to see how it has potentially been affected by changes in the explanatory variable. In our context, growth hormone levels or the physical growth of children is the response variable. It is 'dependent' because its variation is hypothesized to rely on the changes induced in the explanatory variable (amount of sleep).

When planning an experiment, it is imperative to accurately measure the response variable to collect reliable data. In the scenario of assessing children's growth, researchers would systematically record growth metrics over time to determine if a lack of sleep correlates with stunted growth. The integrity of an experiment largely hinges on the precise observation and recording of this variable, as it directly reflects the outcome of the imposed experimental conditions.

Ethical Considerations in Experiments

Experiments, particularly those involving human subjects, must be conducted within ethical boundaries to ensure the well-being and rights of participants are protected. When the subject matter touches sensitive areas such as children's health or necessitates intervening in natural processes like sleep, ethical implications become even more pronounced. Sleep is a fundamental human need, and its deprivation, especially in children, is linked with various negative health outcomes, making such an experiment ethically concerning.

To conduct ethical research, investigators must respect principles such as informed consent, minimize potential harm, and ensure the privacy of participants. In the case of a study involving sleep restriction, the potential for harm not only disqualifies the research from an ethical standpoint but may also make the findings unreliable due to the unethical treatment of subjects. Therefore, when considering experiments with factors that could cause physical or psychological harm, researchers must seek alternative methods or observational studies that do not involve direct intervention, to uphold ethical standards of scientific inquiry.