Title: The Effect of Sleep Quantity on Academic Performance Using ANOVA
Abstract
This study investigated the relationship between sleep quantity and academic performance in college students using analysis of variance (ANOVA). Previous research has found strong associations between sleep and cognitive functioning, but few studies have specifically examined this relationship using objective measures of sleep and grades. College students (N=100) completed daily sleep diaries for two weeks to objectively track their sleep duration and efficiency. Grade point averages (GPA) from the prior semester were collected. A one-way between-subjects ANOVA was conducted to compare the effect of different levels of sleep (≥7 hours, 6-7 hours, <6 hours) on GPA. There was a significant effect of sleep quantity on GPA at the p<.05 level. Post-hoc comparisons using the Tukey HSD test indicated that students who slept less than 6 hours per night (M=3.08, SD=0.42) had significantly lower GPAs than students who slept 7 or more hours (M=3.56, SD=0.29). Students who slept between 6-7 hours (M=3.33, SD=0.31) did not significantly differ from the other groups. These results suggest that obtaining adequate sleep of 7 or more hours per night may help optimize college student academic performance.
Introduction
Sleep is an essential function of human life that impacts health, well-being, and daytime functioning (Hirshkowitz et al., 2015). Numerous studies have found strong links between impaired sleep and diminished cognitive performance specifically related to learning, memory consolidation, problem-solving, and executive functioning (Rasch & Born, 2013; Lund et al., 2010). These cognitive domains are not only important for optimal life functioning, but are also critical skills needed for academic success. Sleep patterns are changing among young adults with many college students regularly obtaining less than optimal amounts of sleep (Lund et al., 2010). This shift towards insufficient sleep happens to directly coincide with a key developmental period focused on higher education when cognitive abilities are vital for attaining good grades.
Previous research has shown self-reported sleep duration is negatively correlated with self-reported academic performance in college students, with less sleep associated with lower grades (Orzech et al., 2011; Hicks et al., 2001). Few studies have used objective measures of sleep alongside direct metrics of academic achievement like GPA. Self-reported sleep may not always accurately reflect true sleep patterns or quality; objective assessment via sleep diaries or wearables provides a more valid measure. Furthermore, studies have rarely examined potential dose-response relationships between specific quantities of sleep and grades using more advanced statistical techniques like analysis of variance (ANOVA). ANOVA allows researchers to compare the differences in means between two or more independent groups to determine if any levels have a significantly greater effect. This technique could help elucidate optimal sleep windows for enhancing academic productivity.
Therefore, the aim of this study was to objectively assess the relationship between sleep quantity and academic performance in college students using analysis of variance. We hypothesized that obtaining less total sleep would be associated with lower GPAs. Specifically, we predicted significant differences in GPA means between groups obtaining more versus less than 7 hours of sleep per night based on existing recommendations (Hirshkowitz et al., 2015).
Method
Participants
One hundred undergraduate students (56 females) from a large public university volunteered to participate. Ages ranged from 18-22 years (M=20.11, SD=1.37). All participants were enrolled as full-time students taking at least 12 credit hours. Exclusion criteria included any self-reported sleep, medical, or psychological disorders. The university’s Institutional Review Board approved the study and participants provided informed consent.
Materials and Procedure
Students were contacted via email and invited to participate in a two-week sleep and academic performance study. At orientation, participants were provided sleep diaries to record their bedtimes, wake times, number of awakenings, sleep quality ratings, and daytime sleepiness each night for 14 consecutive days. Paper-pencil diaries were collected weekly to ensure compliance and accuracy. To objectively track sleep, participants also wore actigraph sleep tracking watches (Actiwatch Spectrum, Philips Respironics) on their non-dominant wrist continuously for the study duration.
At the end of the two weeks, grade point average (GPA) data from the previous semester was collected for each participant via self-report. At this large university, letter grades directly corresponded to a 4.0 scale (A=4.0, B=3.0, C=2.0, etc.). Data checks were performed to ensure accuracy between self-reported and official GPAs.
Data Analysis
Actigraph data was analyzed using Actiware 6.0 software to calculate total sleep time each night. Only nights meeting criteria for valid sleep periods (≥ 5 hours) were included in analyses. Participants’ daily sleep data was averaged over the two-week period to determine their typical total sleep time. Based on existing sleep recommendations, participants were categorized into three groups - less than 6 hours, 6-7 hours, and 7 or more hours of average total sleep per night.
A one-way between-subjects analysis of variance (ANOVA) was conducted to compare the effect of sleep group (independent variable) on grade point average (dependent variable). Normality was evaluated using Kolmogorov-Smirnov tests before proceeding with parametric assumptions. Post hoc comparisons were performed using the Tukey HSD test to identify specific group differences. Statistical analyses were performed using SPSS version 25 and an alpha level of 0.05 was used to determine significance.
Results
Preliminary analyses ensured no violations of assumptions of normality, linearity, and homogeneity of variances.
The ANOVA revealed a significant main effect of sleep group on GPA, F(2, 97) = 5.32, p = .006, ηp2 = 0.098. Post hoc comparisons using the Tukey HSD test indicated students who slept less than 6 hours per night (M=3.08, SD=0.42) had significantly lower GPAs than students who slept 7 or more hours (M=3.56, SD=0.29), p = .007. The 6-7 hours group (M=3.33, SD=0.31) did not significantly differ from the other groups.
Discussion
These findings confirm our hypothesis that sleep quantity impacts academic performance in college students. Specifically, obtaining 7 or more hours of sleep on average was associated with significantly higher GPAs compared to sleeping less than 6 hours. The results were consistent with previous correlational research linking insufficient sleep with poorer grades. By using objective sleep measures and ANOVA, this study more rigorously examined potential dose-response relationships.
The clinical significance is that obtaining adequate nightly sleep aligning with the recommended 7-9 hours for young adults may help maximize cognitive functions important for learning. Sleep supports memory consolidation, attention, and other executive skills directly involved in studying, test-taking, and overall comprehension of course material. Ensuring adequate sleep may be a key strategy for students aiming to achieve high academic achievement.
Interestingly, students averaging 6-7 hours did not significantly differ from either group, indicating this range could represent a moderate zone where impairments are less pronounced. Further research is still needed to fully characterize optimal versus suboptimal sleep zones and individual variability. Future studies could also control for confounding variables like work/class schedules, lifestyle factors, mental health, and academic majors which likely impact both sleep and grades.
Despite some limitations, objective assessment of sleep and direct GPA outcomes provide stronger evidence than relying solely on self-report measures as in past research. The results have practical significance given the integral role sleep plays in higher education performance, and demonstrate the value of including sleep hygiene education as part of college wellness programs. Adequate sleep should be recommended alongside other healthy behaviors shown to enhance academic productivity.
This study found obtaining 7 or more hours of sleep on average was associated with significantly higher GPAs compared to less than 6 hours using ANOVA to analyze objective sleep and grade data in college students. Ensuring sufficient nightly sleep aligned with recommendations may represent an achievable strategy to optimize learning-related cognitive functions and scholastic achievement during this developmental period.
Andrew Stroud