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Running and sleep. Sufficient sleep is important for adolescents for both their neural and psychological development. Despite this, daytime sleepiness and poor physical and psychological functioning related to chronic sleep disturbances are common. There is a growing body of evidence that exercise is associated with both better sleep and improved psychological functioning. Sixty participants were recruited from a high school in northwestern Switzerland. They were randomly assigned to either a running group or a control group, 30 to each group. The running group ran every moming for a little over 30 minutes on weekdays for a three-week period. All participants used a sleep log for subjective evaluation of sleep, and sleep was also objectively assessed at the beginning and end of the study using a sleep electroencephalographic device that measured quantities such as sleep efficiency and time spent in the four different sleep phases. Running was found to have a positive impact on both objective and subjective measures of sleep functioning. \({ }^{24}\) (a) What are the explanatory variable(s) and the response variable(s)? (b) Outline the design of the experiment. (c) Here are some more details on the treatment and control groups. All participants arrived at school at 7 a.m., and the running group did two laps on the track and then ran cross country in groups of at least four people for 30 minutes. The control group remained seated at the track, worked on homework, and interacted with each other. When the runners retumed, all participants prepared for school and ate a breakfast that was provided. Why do you think the experimenters had the control group arrive at 7 a.m., interact with classmates, and have breakfast together? Explain. Do you think having the control group do these activities is important for the types of conclusions that can be reached? How? (d) Time to sleep onset was measured before the beginning of the study and again at the end of the study for participants in both groups. Can this be considered a randomized controlled experiment with time to sleep onset as the response and four treatments (runners before, runners after, controls before, and controls after)? Explain why or why not.

Step by step solution

01

Identify Explanatory and Response Variables

The explanatory variable in the given study is the activity level of the participants, specifically whether they are engaged in the running program (running group) or not (control group). The response variables are the measures of sleep quality, including both objective measures (such as sleep efficiency and time spent in different sleep phases using EEG devices) and subjective sleep evaluations using a sleep log.

02

Outline Experiment Design

The experiment is designed by randomly assigning 60 participants into two groups: a running group and a control group, each consisting of 30 participants. The running group participated in a morning running session for over 30 minutes every weekday for three weeks, while the control group did not participate in these sessions. Sleep was evaluated both subjectively through sleep logs and objectively via EEG devices at the start and conclusion of the study.

03

Justify Activities for Control Group

The experiment had the control group arrive at 7 a.m., interact with each other, and have breakfast together to maintain consistent conditions between both groups, excluding the physical exercise. This helps to control for any potential social or time-of-day related effects on sleep quality or psychological functioning, thereby isolating the impact of running more effectively. This is important for ensuring that any differences observed can be attributed to the exercise itself rather than other factors such as social interaction or breakfast intake.

04

Assess Randomized Controlled Experiment Design

The study cannot be considered a randomized controlled trial with four treatments for sleep onset time since it does not involve four different interventions. Instead, it involves one intervention (running) with pre- and post-intervention measurements. The design involves measuring time to sleep onset at the start and end for each group, and thus maintains a simple comparative format between two conditions rather than four distinct treatments.

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Key Concepts

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

Explanatory Variables

In an experiment, explanatory variables are also known as independent variables. These are the variables that are manipulated or categorized to observe their effect on the outcome. In the study about running and sleep, the explanatory variable is the activity level of the participants. This is specifically defined by whether participants are part of the running group or the control group. The activity level becomes a determinant factor that may influence the outcomes concerning sleep quality. In simpler terms, we're examining how the differences in physical activity (running versus no running) affect the sleep patterns of adolescents.
By manipulating the activity level, researchers attempt to isolate its effects, differentiating between natural variations in sleep quality and those attributed to the structured intervention of daily morning runs. This clear distinction helps in understanding the causal relationship between increased physical activity and improvements in sleep quality.

Response Variables

Response variables, often termed dependent variables, are the outcomes that researchers measure in an experiment. They show the effects of the explanatory variables. In this experiment related to adolescent sleep, the response variables are the various measures of sleep quality. Both objective and subjective evaluations are employed here.
Objective measures involve utilizing a sleep electroencephalographic (EEG) device to assess sleep efficiency and quantify the time spent in different sleep phases. This provides precise, measurable data on how well the participants are sleeping. On the other hand, subjective measures are gathered through sleep logs where participants record their own perceptions of sleep quality. This could include self-reported figures like how long they think they sleep and how rested they feel.
These diverse metrics offer a comprehensive understanding of how the explanatory variable—physical activity—affects sleep, allowing for a more informed conclusion about the relationship between exercise and sleep quality in adolescents.

Randomized Controlled Trial

A randomized controlled trial (RCT) is a fundamental experimental design that minimizes bias by randomly allocating subjects into different groups: intervention (or treatment) and control. This randomization is crucial for validating the results because it aims to equilibrate both known and unknown factors among the participants, creating a level playing field.
In the context of this experiment, 60 high school students were randomly divided into two even groups. One group participated in a running program while the other did not. This random allocation helps ensure that any observed differences in sleep quality are likely due to the running activity rather than external variances between the groups.
However, it is important to note that while this study involves randomization, it should not be mistaken for a trial with multiple interventions or treatments. The fundamental intervention was the running activity, with measurements taken before and after the intervention period. This layout underscores the essence of RCTs in scientific research: isolating the actual impact of the intervention, devoid of confounding factors.

Sleep Quality Measurement

Evaluating sleep quality in a scientific setting involves both subjective and objective assessments to capture a holistic view of an individual’s sleep experience. This study utilized two main tools: sleep logs and EEG devices.
Sleep logs are a subjective method, allowing participants to record details about their sleep. These could include estimated sleep duration, perceived restfulness, and other sleep-related feelings and experiences. Such logs rely on the participant's perception and personal assessment of their sleep. They are particularly valuable for gaining insights into how participants feel about their sleep and any changes they notice themselves.
EEG devices, in contrast, provide objective data by measuring electrical activity in the brain to determine stages of sleep. These measurements can include sleep efficiency (the ratio of time spent asleep compared to the time spent in bed trying to sleep) and the duration of various sleep phases (like REM sleep or deep sleep).
Combining these tools allows researchers to cross-reference perceived sleep quality with actual sleep data, thus providing a robust analysis of how interventions like running influence overall sleep patterns and quality in adolescents.