Imputing accelerometer non-wear time when assessing children's moderate-to-vigorous physical activity

BACKGROUND: Moderate-to-vigorous physical activity (MVPA) is an important determinant of children’s physical health, and is commonly measured using accelerometers. A major limitation of accelerometers is non-wear time, which is the time the participant did not wear their device. Given that non-wear time is traditionally discarded from the dataset prior to estimating MVPA, final estimates of MVPA may be biased. Therefore, alternate approaches should be explored. OBJECTIVES: The objectives of this thesis were to 1) develop and describe an imputation approach that uses the socio-demographic, time, health, and behavioural data from participants to replace non-wear time accelerometer data, 2) determine the extent to which imputation of non-wear time data influences estimates of MVPA, and 3) determine if imputation of non-wear time data influences the associations between MVPA, body mass index (BMI), and systolic blood pressure (SBP). METHODS: Seven days of accelerometer data were collected using Actical accelerometers from 332 children aged 10-13. Three methods for handling missing accelerometer data were compared: 1) the “non-imputed” method wherein non-wear time was deleted from the dataset, 2) imputation dataset I, wherein the imputation of MVPA during non-wear time was based upon socio-demographic factors of the participant (e.g., age), health information (e.g., BMI), and time characteristics of the non-wear period (e.g., season), and 3) imputation dataset II wherein the imputation of MVPA was based upon the same variables as imputation dataset I, plus organized sport information. Associations between MVPA and health outcomes in each method were assessed using linear regression. RESULTS: Non-wear time accounted for 7.5% of epochs during waking hours. The average minutes/day of MVPA was 56.8 (95% CI: 54.2, 59.5) in the non-imputed dataset, 58.4 (95% CI: 55.8, 61.0) in imputed dataset I, and 59.0 (95% CI: 56.3, 61.5) in imputed dataset II. Estimates between datasets were not significantly different. The strength of the relationship between MVPA with BMI and SBP were comparable between all three datasets. CONCLUSION: These findings suggest that studies that achieve high accelerometer compliance with unsystematic patterns of missing data can use the traditional approach of deleting non-wear time from the dataset to obtain MVPA measures without substantial bias.

"Can you ask her to help?" An examination of the factors that promote and discourage prosocial intervention in preschool children

Previous research has examined young children’s ability to detect who would be most likely to provide help to others in a given situation, but little is known about their ability to intervene based on this knowledge in a real-life setting. In the current study, 48 three-year-old children chose between two actors to retrieve an out-of-reach object for the Experimenter; one actor was physically incapable of providing the object (blocked by a tall barrier), and one was capable. Participants’ looking behaviour between the two actors during the study was also recorded and analyzed as an additional, nonverbal measure of their prediction about who would help. Approximately half of the participants in the sample actively intervened on behalf of the Experimenter, but only after a direct request for help was made. Though the other participants did not engage in this helping behaviour, they chose the unblocked actor to help the Experimenter in a subsequent interview. Children also spent more time looking at the unblocked actor. Secondary analyses indicated that shyness prevented many children in the study from asking for help on behalf of the Experimenter from one of the actors. Finally, an unexpected side bias for looking behaviour toward the actors was found that has implications for how the study design could be improved for future research.

RELIBILITY ANALYSIS OF SIMPLE SLOPES AND SOIL-STRUCTURES WITH LINEAR LIMIT STATES

The first objective of this research was to develop closed-form and numerical probabilistic methods of analysis that can be applied to otherwise conventional methods of unreinforced and geosynthetic reinforced slopes and walls. These probabilistic methods explicitly include random variability of soil and reinforcement, spatial variability of the soil, and cross-correlation between soil input parameters on probability of failure. The quantitative impact of simultaneously considering the influence of random and/or spatial variability in soil properties in combination with cross-correlation in soil properties is investigated for the first time in the research literature. Depending on the magnitude of these statistical descriptors, margins of safety based on conventional notions of safety may be very different from margins of safety expressed in terms of probability of failure (or reliability index). The thesis work also shows that intuitive notions of margin of safety using conventional factor of safety and probability of failure can be brought into alignment when cross-correlation between soil properties is considered in a rigorous manner. The second objective of this thesis work was to develop a general closed-form solution to compute the true probability of failure (or reliability index) of a simple linear limit state function with one load term and one resistance term expressed first in general probabilistic terms and then migrated to a LRFD format for the purpose of LRFD calibration. The formulation considers contributions to probability of failure due to model type, uncertainty in bias values, bias dependencies, uncertainty in estimates of nominal values for correlated and uncorrelated load and resistance terms, and average margin of safety expressed as the operational factor of safety (OFS). Bias is defined as the ratio of measured to predicted value. Parametric analyses were carried out to show that ignoring possible correlations between random variables can lead to conservative (safe) values of resistance factor in some cases and in other cases to non-conservative (unsafe) values. Example LRFD calibrations were carried out using different load and resistance models for the pullout internal stability limit state of steel strip and geosynthetic reinforced soil walls together with matching bias data reported in the literature.

EDUCATING THE PUBLIC THROUGH NEWS MEDIA: CASE STUDIES OF NEWS LITERACY IN THE NEW MEDIA LANDSCAPE

Two decades of unprecedented changes in the media landscape have increased the complexity of informing the public through news media. With significant changes to the way the news industry does business and the way news consumers access this information, a new set of skills is being proposed as essential for today’s news consumer. News literacy is the use of critical thinking skills to assess the reliability and source of the information that people consume on a daily basis, as well as fostering self-awareness of personal news consumption habits and how it can create audience bias. The purpose of this study was to examine how adults experience the news in their everyday lives and to describe the nature of the news literacy skills people employ in their daily news consumption. This study purposefully selected four adults who have completed high school, and who regularly consume news information across a number of platforms, both traditional and digital. Two of the participants, one man and one woman, were over 50 years old. One other male participant was in his 30’s and the final participant, a young woman, was in her 20’s. They all utilized both traditional and digital media on a regular basis and all had differing skill levels when using social media for information. Their news experiences were documented by in-depth interviews and the completion of seven daily news logs. In their daily logs the participants differentiated news information from other information available on-line but the interviews revealed a contradiction between their intentions and their news consumption practices. All four participants had trouble distinguishing between news and opinion pieces in the news information realm. In addition all but one seemed unaware of their personal bias and any possible effect it was having on their news consumption. Further research should explore the benefits of an adult-centered news literacy curriculum on news consumers similar to the participants, and should examine the development of audience bias and its relationship to the daily exposure people have to the torrent of information that is available to them on a daily basis.

Investigating Multiple Roles of Vocal Confidence in Persuasion

Although persuasion often occurs via oral communication, it remains a comparatively understudied area. This research tested the hypothesis that changes in three properties of voice influence perceptions of speaker confidence, which in turn differentially affects attitudes according to different underlying psychological processes that the Elaboration Likelihood Model (ELM, Petty & Cacioppo, 1984), suggests should emerge under different levels of thought. Experiment 1 was a 2 (Elaboration: high vs. low) x 2 (Vocal speed: increased speed vs. decreased speed) x 2 (Vocal intonation: falling intonation vs. rising intonation) between participants factorial design. Vocal speed and vocal intonation influenced perceptions of speaker confidence as predicted. In line with the ELM, under high elaboration, confidence biased thought favorability, which in turn influenced attitudes. Under low elaboration, confidence did not bias thoughts but rather directly influenced attitudes as a peripheral cue. Experiment 2 used a similar design as Experiment 1 but focused on vocal pitch. Results confirmed pitch influenced perceptions of confidence as predicted. Importantly, we also replicated the bias and cue processes found in Experiment 1. Experiment 3 investigated the process by which a broader spectrum of speech rate influenced persuasion under moderate elaboration. In a 2 (Argument quality: strong vs. weak) x 4 (Vocal speed: extremely slow vs. moderately slow vs. moderately fast vs. extremely fast) between participants factorial design, results confirmed the hypothesized non-linear relationship between speech rate and perceptions of confidence. In line with the ELM, speech rate influenced persuasion based on the amount of processing. Experiment 4 investigated the effects of a broader spectrum of vocal intonation on persuasion under moderate elaboration and used a similar design as Experiment 3. Results indicated a partial success of our vocal intonation manipulation. No evidence was found to support the hypothesized mechanism. These studies show that changes in several different properties of voice can influence the extent to which others perceive them as confident. Importantly, evidence suggests different vocal properties influence persuasion by the same bias and cue processes under high and low thought. Evidence also suggests that under moderate thought, speech rate influences persuasion based on the amount of processing.

Polymer Light-Emitting Electrochemical Cells with Embedded Bipolar Electrodes: Visualizing Bipolar Electrochemistry in Solid State

The work presented in this thesis examines the properties of BPEs of various configurations and under different operating conditions in a large planar LEC system. Detailed analysis of time-lapsed fluorescence images allows us to calculate the doping propagation speed from the BPEs. By introducing a linear array of BPEs or dispersed ITO particles, multiple light-emitting junctions or a bulk homojunction have been demonstrated. In conclusion, it has been observed that both applied bias voltages and sizes of BPEs affected the electrochemical doping from the BPE. If the applied bias voltage was initially not sufficiently high enough, a delay in appearance of doping from the BPE would take place. Experiments of parallel BPEs with different sizes (large, medium, small) demonstrate that the potential difference across the BPEs has played a vital role in doping initiation. Also, the p-doping propagation distance from medium-sized BPE has displayed an exponential growth over the time-span of 70 seconds. Experiments with a linear array of BPEs with the same size demonstrate that the doping propagation speed of each floating BPE was the same regardless of its position between the driving electrodes. Probing experiments under high driving voltages further demonstrated the potential of having a much more efficient light emission from an LEC with multiple BPEs.