Certificate validation is today a vital part of keeping communication secure over the internet. It allows secure daily communication for roughly 5 billion people using the internet. This is done by the help of Certificate Authorities, who use the technique of certificate validation chains for a more relentless validation and to widen the possibilities of secure communication. These chains have been in a changing process since the beginning, which has not been in a single direction. In this thesis, the changes in properties of the certificate chains are studied during the time period 2013 until 2021. The datasets of certificate chains are generated from the crt.sh database. The focus is put on finding changes in the length of the certificate chains and where in the chains these changes appear. Being able to understand and explain these changes is of great value in order to know about the further development of these chains and to predict the future direction that these chains might take. Based on the findings from the analysis of the chains included in the dataset, it was possible to conclude that the average length of the chains has increased over the time period. Though there have been special occasions in the industry-leading to decline in later years of the time period.The findings in this thesis indicates that what is important for the industry has changed. From having a focus on increasing the length to shift focus to shorten the length to provide better performance in terms of speed.

The satellite-based cloud condensation nuclei (CCN) proxies used to quantify the aerosolcloud interactions (ACIs) are column integrated and do not guarantee the vertical co-location of aerosols and clouds. This has encouraged the use of height-resolved measurements of spaceborne lidars for ACI studies and led to advancements in lidar-based CCN retrieval algorithms. In this study, we present a comparison between the number concentration of CCN (nCCN) derived from ground-based in situ and spaceborne lidar cloud-aerosol lidar with orthogonal polarization (CALIOP) measurements. On analysing their monthly time series, we found that about 88% of CALIOP nCCN estimates remained within a factor of 1.5 of the in situ measurements. Overall, the CALIOP estimates of monthly nCCN were in good agreement with the in situ measurements with a normalized mean error of 71%, normalized mean bias of 39% and correlation coefficient of 0.68. Based on our comparison results, we point out the necessary measures that should be considered for global nCCN retrieval. Our results show the competence of CALIOP in compiling a global height- and type-resolved nCCN dataset for use in ACI studies.

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This study aimed to develop and validate a rating scale for assessing English First Additional Language essays at Grade 12 level for the final National Senior Certificate examination. The importance of writing as a communicative skill is emphasised with the re-introduction of writing as Paper 3 of the English First Additional Language examination at the end of Grade 12 in South Africa. No empirical evidence, however, is available to support claims of validity for the current rating scale. The literature on the concept of validity and the process of validation was surveyed. Theoretical models and validation frameworks were evaluated to establish a theoretical base for the development and validation of a rating scale for assessing writing. The adopted framework was used to evaluate the adequacy of the current rating scale used for assessing Grade 12 writing in South Africa. The current scale was evaluated in terms of the degree to which it offers an appropriate means of assessing Grade 12 Level essay writing while adhering to requirements of the National Curriculum Statement. It was found lacking and the need for a new, validated rating scale was established. Various approaches to scale development were considered in consideration of factors that impact scores directly, viz. the type of rating scale, rater characteristics, scoring procedures and rater training. A new scale was developed and validated following an empirical procedure comprising four phases. The empirical process was based on an analysis of actual performances of Grade 12 English learner writing. A combination of quantitative and qualitative methods was used in each of the four phases to ensure the validity of the instrument. The outcome of this project was an empirically developed and validated multiple trait rating scale to assess Grade 12 essay writing. The proposed scale distinguishes five criteria assessed by means of a seven-point scale. / Thesis (Ph.D. (English))--North-West University, Potchefstroom Campus, 2009.

This study aimed to develop and validate a rating scale for assessing English First Additional Language essays at Grade 12 level for the final National Senior Certificate examination. The importance of writing as a communicative skill is emphasised with the re-introduction of writing as Paper 3 of the English First Additional Language examination at the end of Grade 12 in South Africa. No empirical evidence, however, is available to support claims of validity for the current rating scale. The literature on the concept of validity and the process of validation was surveyed. Theoretical models and validation frameworks were evaluated to establish a theoretical base for the development and validation of a rating scale for assessing writing. The adopted framework was used to evaluate the adequacy of the current rating scale used for assessing Grade 12 writing in South Africa. The current scale was evaluated in terms of the degree to which it offers an appropriate means of assessing Grade 12 Level essay writing while adhering to requirements of the National Curriculum Statement. It was found lacking and the need for a new, validated rating scale was established. Various approaches to scale development were considered in consideration of factors that impact scores directly, viz. the type of rating scale, rater characteristics, scoring procedures and rater training. A new scale was developed and validated following an empirical procedure comprising four phases. The empirical process was based on an analysis of actual performances of Grade 12 English learner writing. A combination of quantitative and qualitative methods was used in each of the four phases to ensure the validity of the instrument. The outcome of this project was an empirically developed and validated multiple trait rating scale to assess Grade 12 essay writing. The proposed scale distinguishes five criteria assessed by means of a seven-point scale. / Thesis (Ph.D. (English))--North-West University, Potchefstroom Campus, 2009.

With the explosion in usage of big data, stakes are high for companies to develop workflows that translate the data into business value. Those data transformations are continuously updated and refined in order to meet the evolving business needs, and it is imperative to ensure that a new version of a workflow still produces the correct output. This study focuses on the validation of big data in a real-world scenario, and implements a validation tool that compares two databases that hold the results produced by different versions of a workflow in order to detect and prevent potential unwanted alterations, with row-based and column-based statistics being used to validate the two versions. The tool was shown to provide accurate results in test scenarios, providing leverage to companies that need to validate the outputs of the workflows. In addition, by automating this process, the risk of human error is eliminated, and it has the added benefit of improved speed compared to the more labour-intensive manual alternative. All this allows for a more agile way of performing updates on the data transformation workflows by improving on the turnaround time of the validation process.

The world of work has become extremely volatile, with the scarcity of skills and the management of human capital at the top of the agenda. Human capital is the most valuable asset in any organisation. It is evident that leadership is vital in organisations in ensuring their success; thus making leadership empowerment behaviour crucial. It is essential that our leaders become people developers who focus on growing and up skilling subordinates as a way of attracting and retaining talent. It is important that leaders create an enabling environment for their subordinates; one of independence, innovation and, more importantly, growth and development. The purpose of this study was to explore the psychometric properties of the leadership empowerment questionnaire by investigating internal consistency; furthermore investigating the differences between genders regarding male and female perceptions of leadership empowerment behaviour. A quantitative cross-sectional survey was used. The measuring battery comprised the Leadership Empowerment Behaviour Questionnaire (LEBQ), which is originally a six-factor structure. The analysis was carried out using the IBM-SPSS and Mplus statistical modelling programs. Reliability was explored by utilising the Confirmatory Factor Analysis (CFA) index (rho). Construct validity was assessed by examining the factor structure, utilising the Exploratory Factor Analysis (EFA) and the CFA. Satisfactory reliability indices were attained. A three-factor model of the LEBQ was confirmed. The three-factor model consists of autonomy, development and accountability. Measurement invariance was tested by the use of configural, scalar and metric invariance. The configural model concluded that the three-factor structure obtained for the total sample also holds for the two groups (Males & Females) of respondents separately. The metric model indicates that the latent variables are measured in the same way with the same metric in the two target groups. The Scalar model indicates that on these three items, males and females differ regarding their starting points in their response to these questions. Although there were differences in the starting points of certain items, there were no real differences evident in the overall model regarding males and females. Recommendations for further research were made. / MA (Industrial Psychology)--North-West University, Vaal Triangle Campus, 2015

In psychology and other related fields, the study of meaning in life has shown a re-emergence of scientific interest (e.g. Hicks & King, 2009; Ho, Cheung & Cheung, 2010; Steger, Oishi & Kashdan, 2009; Wong, 2011). The recent increase in interest may be attributed to the links made to positive psychological and health outcomes, such as: psychological strengths, subjective well-being and hope amongst others (Diener, 2000; Diener & Ryan, 2009; Fredrickson, 2000; Snyder, 2002; Ungar, 2008, 2011). Research has also shown that a lack of meaning in life has been linked to negative psychological outcomes (Steger et al., 2006; Zika & Chaimberlain, 1992). Whilst authors agree that meaning in life is important the conceptualisation of meaningfulness has been conflicted (Auhagen, 2000). More recently Steger and his colleagues (2006) have conceptualised that meaning in life consists of two inter-dependent constructs; namely the presence of meaning in life and the search for meaning in life. The presence of meaning in life is defined as “the extent to which people comprehend, make sense of and see significance in their lives, accompanied by the degree to which they perceive themselves to have a purpose, mission or overarching aim in life”; and the search for meaning in life refers to the “degree to which people are trying to establish and/or augment their comprehension of meaning in life, significance and purpose” (Steger et al., 2006). Based on this conceptualisation Steger et al. (2006) have developed the MLQ (Meaning in Life Questionnaire) with two separate but interrelated constructs; the Presence of Meaning in life (5-items) and the Search for Meaning in life (5-items). The items of the measure are measured on a 7-point Likert-scale where participants are required to state their agreement with statements ranging from 1 (Absolutely untrue) to 7 (Absolutely true). The aim of this study was to investigate the psychometric properties of the Meaning in Life Questionnaire (Steger et al., 2006) as a measure of the Search for and Presence of Meaning in life so as to validate the scale in an African context. In an endeavour to validate this scale a multicultural group of students from the North-West University in South Africa (n=326) recruited by their lecturers, completed a set of questionnaires. Most of the participants were female (n=243, 74.5%), while male participants made up 24.5% of the sample. The results of this study are in support of the scale’s reliability and validity in an African context. Confirmatory factor analysis confirms the goodness of fit of the scale. The two factor structure was favoured. In conclusion, future research should also investigate the measurement equivalence of the MLQ on the basis of language (see Hambleton & Zenisky, 2011; Van de Vijver & Leung, 2011). Measurement equivalence and item response theory studies may provide evidence on whether there are cross-cultural and language differences in how participants interpret and respond to the MLQ items. One might also assess relationships between meaning in life and positive functioning indicators in this sample. / MSc (Clinical Psychology), North-West University, Potchefstroom Campus, 2014

In psychology and other related fields, the study of meaning in life has shown a re-emergence of scientific interest (e.g. Hicks & King, 2009; Ho, Cheung & Cheung, 2010; Steger, Oishi & Kashdan, 2009; Wong, 2011). The recent increase in interest may be attributed to the links made to positive psychological and health outcomes, such as: psychological strengths, subjective well-being and hope amongst others (Diener, 2000; Diener & Ryan, 2009; Fredrickson, 2000; Snyder, 2002; Ungar, 2008, 2011). Research has also shown that a lack of meaning in life has been linked to negative psychological outcomes (Steger et al., 2006; Zika & Chaimberlain, 1992). Whilst authors agree that meaning in life is important the conceptualisation of meaningfulness has been conflicted (Auhagen, 2000). More recently Steger and his colleagues (2006) have conceptualised that meaning in life consists of two inter-dependent constructs; namely the presence of meaning in life and the search for meaning in life. The presence of meaning in life is defined as “the extent to which people comprehend, make sense of and see significance in their lives, accompanied by the degree to which they perceive themselves to have a purpose, mission or overarching aim in life”; and the search for meaning in life refers to the “degree to which people are trying to establish and/or augment their comprehension of meaning in life, significance and purpose” (Steger et al., 2006). Based on this conceptualisation Steger et al. (2006) have developed the MLQ (Meaning in Life Questionnaire) with two separate but interrelated constructs; the Presence of Meaning in life (5-items) and the Search for Meaning in life (5-items). The items of the measure are measured on a 7-point Likert-scale where participants are required to state their agreement with statements ranging from 1 (Absolutely untrue) to 7 (Absolutely true). The aim of this study was to investigate the psychometric properties of the Meaning in Life Questionnaire (Steger et al., 2006) as a measure of the Search for and Presence of Meaning in life so as to validate the scale in an African context. In an endeavour to validate this scale a multicultural group of students from the North-West University in South Africa (n=326) recruited by their lecturers, completed a set of questionnaires. Most of the participants were female (n=243, 74.5%), while male participants made up 24.5% of the sample. The results of this study are in support of the scale’s reliability and validity in an African context. Confirmatory factor analysis confirms the goodness of fit of the scale. The two factor structure was favoured. In conclusion, future research should also investigate the measurement equivalence of the MLQ on the basis of language (see Hambleton & Zenisky, 2011; Van de Vijver & Leung, 2011). Measurement equivalence and item response theory studies may provide evidence on whether there are cross-cultural and language differences in how participants interpret and respond to the MLQ items. One might also assess relationships between meaning in life and positive functioning indicators in this sample. / MSc (Clinical Psychology), North-West University, Potchefstroom Campus, 2014

The world of work has become extremely volatile, with the scarcity of skills and the management of human capital at the top of the agenda. Human capital is the most valuable asset in any organisation. It is evident that leadership is vital in organisations in ensuring their success; thus making leadership empowerment behaviour crucial. It is essential that our leaders become people developers who focus on growing and up skilling subordinates as a way of attracting and retaining talent. It is important that leaders create an enabling environment for their subordinates; one of independence, innovation and, more importantly, growth and development. The purpose of this study was to explore the psychometric properties of the leadership empowerment questionnaire by investigating internal consistency; furthermore investigating the differences between genders regarding male and female perceptions of leadership empowerment behaviour. A quantitative cross-sectional survey was used. The measuring battery comprised the Leadership Empowerment Behaviour Questionnaire (LEBQ), which is originally a six-factor structure. The analysis was carried out using the IBM-SPSS and Mplus statistical modelling programs. Reliability was explored by utilising the Confirmatory Factor Analysis (CFA) index (rho). Construct validity was assessed by examining the factor structure, utilising the Exploratory Factor Analysis (EFA) and the CFA. Satisfactory reliability indices were attained. A three-factor model of the LEBQ was confirmed. The three-factor model consists of autonomy, development and accountability. Measurement invariance was tested by the use of configural, scalar and metric invariance. The configural model concluded that the three-factor structure obtained for the total sample also holds for the two groups (Males & Females) of respondents separately. The metric model indicates that the latent variables are measured in the same way with the same metric in the two target groups. The Scalar model indicates that on these three items, males and females differ regarding their starting points in their response to these questions. Although there were differences in the starting points of certain items, there were no real differences evident in the overall model regarding males and females. Recommendations for further research were made. / MA (Industrial Psychology)--North-West University, Vaal Triangle Campus, 2015