Background: Vulnerable populations in Canada shoulder a disproportionately high burden of disease. Transmission of sexually transmitted infections is behaviourally mediated. Previous research indicates an association between depression and sexual risk-taking. Evidence also suggests that social support is an effect modifier. Methods: Data were collected from a population of injection drug users, between 2003 and 2004 in Winnipeg, using respondent driven sampling. Demographic and social behaviors were analyzed to characterize the population, as well as social networks and ego networks. Logistic regression was used to examine the association between depressive symptoms and sexual risk interactions. Social support was examined as an effect modifier. Results: The majority of the study participants and network members were aged between 35 and 44, and a high percentage identified as Native Canadians. The highest percentage of people reported welfare as their primary source of income, and injecting stimulants, as their most frequently injected drug. Logistic regression models indicated an increase in the odds of individuals engaging in high-risk sexual interactions, if they had also self-reported elevated depressive symptoms. It was not possible to conclude that social support was an effect modifier. Conclusion: This research supports a positive association between elevated depressive symptoms, and higher levels of sexual risk interactions. Further research is needed to understand the role of social support.

Target of this dissertation thesis is analyze the respondents in the research Market@Media@Lifestyle, which conducted the Median agency. This work examines the differences between respondents completing the questionnaire thru the internet or paper form. There you can find the information summarized and proposed recommendations for next data use in future in the end of examines, especially for marketing purposes.

This diploma thesis examines the current state of rural tourism in Russia. The aim of this work is to analyze the potential interest among the inhabitants of the Czech Republic and to compare the results with available literature. A part of this thesis is a survey, which by means of the Internet questionnaires investigated the views of the respondents on the given topic. One hundred and two respondents took part in the survey. For the sake of clarity, graphs with individual answers are embedded into the work. The study also includes an assessment of the demand for rural tourism services in Russia. In conclusion, recommendations to owners of businesses, mainly aimed on promotion and advertising are provided.

Psykosomatiska symtom hos barn är mycket utbredda globalt. I olika studier varierar förekomsten av psykosomatiska symtom, delvis på grund av användning av olika datainsamlingsmetoder. En intressant fråga är betydelsen av respondenten. I denna kvantitativa studie jämfördes utvalda psykosomatiska symtom hos barn rapporterade av barnen själva samt rapporterade av deras vårdnadshavare. Studien bygger på data om 4548 barn i årskurs 4 och 7 som insamlades för elevhälsodatabasen ELSA i Värmland. Analysen visade ett svagt samband i rapporteringen av symtom, en stor variation i rapporteringsmönstret främst med avseende på konkret symtom. Sambandet mellan barnens och vårdnadshavarnas rapportering var starkare när det gällde symtomen huvudvärk och magont, för barn i årskurs 7, för flickor, för barn födda i Sverige samt barn med sjukdom/funktionsnedsättning, liksom för barn som inte bor med sina föräldrar samt barn med en vårdnadshavare född utomlands. Resultaten visar genomgående på respondentens stora betydelse för rapporteringens utfall. Val av respondenten måste värderas i förhållande till syftet med informationsinsamling.

The thesis is focused on the evaluation of preferences in organic foods consumption in the Czech Republic. The theoretical part summarizes the insights from the literature concerning the issue. The thesis monitors in detail the production and consumption of organic foods and it maps the market environment. In the practical part were expressed hypotheses which using the questionnaire were confirmed or refuted. They have been also identified preferences of consumer groups of organic foods, which were then analyzed and evaluated. There were performed determinations of prices of selected organic foods in individual retail chains and their subsequent comparison with normal foods.The results of this research may be helpful for new entrants in terms of the market operators to assist them in deciding on which market segment or product to concentrate.

This study investigated the stimulus-reinforcer relations possible in matching-to-sample, and determined the extent that each relation contributed in the transfer to subsequent matching-to-sample. Fifty three homing pigeons were autoshaped on a single key, with two stimuli, red and green. Forty eight subjects were then divided equally in 12 groups receiving the experimental treatments, and five subjects served as no-treatment controls. Group assignments were first based on autoshaping to either an identity, non-identity, or identity and non-identity stimulus relation. Each stimulus relation consisted of a center stimulus followed by an outer key stimulus. For identity, the center and outer stimuli were the same. For non-identity the center and outer stimuli were different, The second aspect determining group divisions was the correlation of reinforcement to the stimulus relation; explicitly paired, explicitly unpaired, truly random, or omission (identity only). The subjects received 10 sessions of autoshaping where each session consisted of 50 exposures to the stimulus sequence correlated with the reinforcement. Subjects were then transferred to an operant task--two color zero-delay matching-to-sample. In matching-to-sample training, the 6-second sample was followed by the presentation of 2 outer key comparison stimuli. The comparisons remained illuminated for 6 seconds or until a response occurred. A response to the matching comparison was reinforced and a response to the non-matching comparison resulted in the inter-trial interval. Sessions consisted of 50 trials. The results from the single stimulus autoshaping sessions revealed that all subjects acquired reliable autoshaping within 150 stimulus-food pairings. The results from the autoshaping sessions revealed that stimulus sequences explicitly paired with food produced reliable responding to both the center and outer stimuli.. No significant differences were observed between center and outer key responding for subjects trained with an explicitly paired food arrangement. Subjects receiving identity stimuli explicitly paired with food and non-identity stimuli explicitly unpaired with food responded differentially to the outer key stimuli, showing control by the identity and non-identity stimulus relations. The truly random, explicitly paired/omission, or explicitly unpaired conditions resulted in center and outer key responses decreasing across sessions. The results from the matching sessions revealed that only autoshaping discrimination training (identity explicitly paired and non-identity explicitly unpaired with food) facilitated transfer to the operant task. Autoshaping training on a single stimulus relation in matching-to-sample (identity or non-identity) did not facilitate matching transfer. The results from the omission training suggest that the key pecking was very susceptible to operant controls. These data were taken to indicate that exposure to and differential responding in the presence of the conditional discriminative stimuli in matching-to-sample may be necessary for matching performance. Exposure and behaving in the presence of components of matching did not produce matching. Therefore any explanation of matching in terms of learning a single stimulus relation rule may be questioned.

It is well understood that substantial health inequality exists for adults with an intellectual disability (AWID). In comparison to the general population AWID experience higher rates of morbidity and mortality associated with sedentary lifestyles, yet little is known about the role physical activity plays in preventing or mediating this outcome for this segment of society. Without appropriate instrumentation, it is not possible to address the inadequacies that currently exist in the area of physical activity and AWID. The primary aim of the series of studies in this thesis was to develop a psychometrically sound proxy-respondent measurement tool that could be used by researchers, epidemiologists and public health personnel to gather information on the physical activity behaviours of AWID. The International Physical Activity Questionnaire (IPAQ) is an internationally published tool with good psychometric properties when used as a self-report tool with adults without a disability (AWOID), but no evidence exists as to the validity or reliability of this tool when used by proxy respondents to report on the physical activity behaviour of AWID. Given little is known about the energy expenditure characteristics of AWID, nor the accuracy of tools developed for AWOID when applied to AWID, two secondary aims of this thesis were to measure the energy expended by AWID and AWOID during seven common activities of daily living (ADL) and to assess the accuracy of an objective physical activity measurement tool (Caltrac® accelerometer) for use with AWID. Evidence gathered through the studies in this thesis found that as the energy demand of ADL increased there was an increase in the difference between energy expended by AWID and AWOID. Results indicated that AWID achieved moderate-intensity physical activity when walking at a pace of 3.0 km/hr or more. The proxy-respondent telephone questionnaire (IPAQ-ID) described in this thesis allows for universal assessment of the physical activity behaviours of AWID. The IPAQ-ID was found to have measurement properties equivalent to measurement tools used among AWOID. The IPAQ-ID was found to be suitable for use as a surveillance tool by researchers to collect comparable data on health-enhancing physical activity behaviours of AWID.

Data that can be represented as a network, where there are measurements both on units and on pairs of units, are becoming increasingly prevalent in the social sciences and public health. Homophily in network data, or the tendency of units to connect based on similar nodal attribute values (i.e. income, HIV status) more often than expected by chance is receiving strong attention from researchers in statistics, medicine, sociology, public health and others. Respondent-Driven Sampling (RDS) is a link-tracing network sampling strategy heavily used in public health worldwide that is cost efficient and allows us to survey populations inaccessible by conventional techniques. Via extensive simulation we study the performance of existing methods of estimating population averages, and show that they have poor performance if there is homophily on the quantity surveyed. We propose the first model-based approach for this setting and show its superiority as a point estimator and in terms of uncertainty intervals coverage rates, and demonstrate its application to a real life RDS-based survey. We study how the strength of homophily effects can be estimated and compared across networks and different binary attributes under several network sampling schemes. We give a proof that homophily can be effectively estimated under RDS and propose a new homophily index. This work moves towards a deeper understanding of network structure as a function of nodal attributes and network sampling under homophily. / Statistics

Master of Science / Department of Statistics / Perla E. Reyes Cuellar / The term network has become part of our everyday vocabulary. The more popular are perhaps the social ones, but the concept also includes business partnerships, literature citations, biological networks, among others. Formally, networks are defined as sets of items and their connections. Often modeled as the mathematic object known as a graph, networks have been studied extensively for several years, and research is widely available. In statistics, a variety of modeling techniques and statistical terms have been developed to analyze them and predict individual behaviors. Specifically, certain statistics like degree distribution, clustering coefficient, and so on are considered important indicators in traditional social network studies. However, while conventional network models assume that the whole network population is known, complete information is not always available. Thus, different sampling methods are often required when the population data is inaccessible. Less time has been dedicated to studying the accuracy of these sampling methods to produce a representative sample. As such, the aim of this report is to identify the capacity of sampling techniques to reflect the features of the original network. In particular, we study Anti-cluster Respondent Driven Sampling (AC-RDS). We also explore whether standard modeling techniques paired with sample data could estimate statistics often used in the study of social networks. Respondent Driven Sampling (RDS) is a chain referral approach to study rare and/or hidden populations. Originating from the link-tracing design, RDS has been further developed into a series of methods utilized in social network studies, such as locating target populations or estimating the number and proportion of needle-sharing among drug addicts. However, RDS does not always perform as well as expected. When the social network contains tight communities (or clusters) with few connections between them, traditional RDS tends to oversample one community, introducing bias. AC-RDS is a special Markov chain process that collects samples across communities, capturing the whole network. With special referral requests, the initial seeds are more likely to refer to the individuals that are outside their communities. In this report, we fitted the Exponential Random Graph Model (ERGM) and a Stochastic Block Model (SBM) to an empirical study of the Facebook friendship network of 1034 participants. Then, given our goal of identifying techniques that will produce a representative sample, we decided to compare two version of AC-RDSs, in addition to traditional RDS, with Simple Random Sampling (SRS). We compared the methods by drawing 100 network samples using each sampling technique, then fitting an SBM to each sample network we used the results to project the network into one of population size. We calculated essential network statistics, such as degree distribution, of each sampling method and then compared the result to the original network observed statistics.

In this diploma thesis a summary of ecological agriculture in Svitavy Region is processed. The first part consists of literary research about description of organic agriculture, its goals, principles, history and legislation and development of this agriculture in the region. In the second part the collected data will be compared with data from other areas in Pardubice Region. Introduction of selected organic farms, producers and sellers of organic food in the region follows. In the final part two surveys are executed. The first questionnaire about knowledge of ecological agriculture and its products is focused on local residents. The second questionnaire is focused on ecological entrepreneurs. In conclusion measures which could lead to improvement of public awareness and to overall development of organic agriculture in Svitavy Region will be suggested.