Zero-inflated count regression models with applications to some examples

In this paper, we employed SAS PROC NLMIXED (Nonlinear mixed model procedure) to analyze three example data having inflated zeros. Examples used are data having covariates and no covariates. The covariates utilized in this article have binary outcomes to simplify our analysis. Of course the analysis can readily be extended to situations with several covariates having multiple levels. Models fitted include the Poisson (P), the negative binomial (NB), the generalized Poisson (GP), and their zero-inflated variants, namely the ZIP, the ZINB and the ZIGP models respectively. Parameter estimates as well as the appropriate goodness-of-fit statistic (the deviance D) in this case are computed and in some cases, the Pearson’s X ² statistic, that is based on the variance of the relevant model distribution is also computed. Also obtained are the expected frequencies for the models and GOF tests are conducted based on the rule established by Lawal (Appl Stat 29:292–298, 1980). Our results extend previous results on the analysis of the chosen data in this example. Further, results obtained are very consistent with previous analyses on the data sets chosen for this article. We also present an hierarchical figure relating all the models employed in this paper. While we do not pretend that the results obtained are entirely new, however, the analyses give opportunities to researchers in the field the much needed means of implementing these models in SAS without having to resort to S-PLUS, R or Stata.     

eLancing: A review and research agenda for bridging the science–practice gap

eLancing, or Internet freelancing, is spreading at an incredibly fast pace worldwide. The eLancing work environment is called a “marketplace,” which is a website where individuals interested in being hired and employers looking for individuals to perform some type of work meet. eLancing allows individuals from literally anywhere in the world to sign up and complete work using the Internet for an employer who literally can also be anywhere in the world. eLancing boasts millions of users and billions of dollars in transactions and it involves fundamental changes in the nature of work and in the employer–worker relationship. We discuss eLancing and challenges and opportunities it creates for human resource management (HRM) research and practice. Also, we offer a research agenda with the goal of understanding eLancing and its effects, particularly pertaining to the core HRM areas of job design and analysis, workforce planning, recruitment, selection, training and development, performance management, compensation, and legal issues. Given the increased importance of eLancing worldwide and its implications for worldwide work arrangements in the 21st century's international society, results of such scholarly research have the potential to help narrow the science–practice gap and also elevate the status, perceived value-added, and organizational and societal influence of HRM and related fields.     

Double symmetry model and its decompositions in square contingency tables having ordered categories

In this paper, we have employed the non-standard log-linear models to fit the double symmetry models and some of its decompositions to square contingency tables having ordered categories. SAS PROC GENMOD was employed to fit these models although we could similarly have used GENLOG in SPSS or GLM in STATA. A SAS macro generates the factor or scalar variables required to fit these models. Two sets of \(4 \times 4\) unaided distance vision data that have been previously analyzed in (Tahata and Tomizawa, Journal of the Japan Statistical Society 36:91–106, 2006) were employed for verification of results. We also extend the approach to the Danish \(5 \times 5\) Mobility data as well as to the \(3 \times 3\) Danish longitudinal study data of subjective health, firstly reported in (Andersen, The Statistical Analysis of Categorical Data, Springer:Berlin, 1994) and analyzed in (Tahata and Tomizawa, Statistical Methods and Applications 19:307–318, 2010). Results obtained agree with those published in previous literature on the subject. The approaches suggest here eliminate any programming that might be required in order to apply these class of models to square contingency tables.     

Characteristics of Private‐Sector Tractor Service Provisions: Insights from Nigeria

Agricultural mechanization has been integral to agricultural transformation during periods of development. Mechanization‐service provisions can be constrained by economies of scale, seasonality, limited mobility, or heterogeneous inputs quality. However, information has been scarce regarding how the private sector has overcome these constraints especially in countries like Nigeria that are at low agricultural development stages. We present the results of a small survey of tractor owner‐operators conducted in Nigeria. We find that existing private‐sector tractor‐hiring services in Nigeria are indeed constrained. However, we also find heterogeneity among these owner‐operators. In particular, those who buy tractors from private markets or from private individuals are more efficient than those who receive tractors through government programs, providing services to a greater area at lower costs, including during off‐peak seasons, sometimes selecting machinery types according to soil types. We conclude with a discussion of some policy implications.     

On fitting the conditional difference asymmetry models to square contingency tables with nominal categories

In this paper, we implement the conditional difference asymmetry model (CDAS) for square tables with nominal categories proposed by Tomizawa et al. (J. Appl. Stat. 31(3): 271–277, 2004) with the use of the non-standard log-linear model formulation approach. The implementation is carried out by refitting the model in the 3 ×  3 table in (Tomizawa et al. J. Appl. Stat. 31(3): 271–277, 2004). We extend this approach to a larger 4 ×  4 table of religious affiliation. We further calculated the measure of asymmetry along with its asymptotic standard error and confidence bounds. The procedure is implemted with SAS PROC GENMOD but can also be implemented in SPSS by following the discussion in (Lawal, J. Appl. Stat. 31(3): 279–303, 2004; Lawal, Qual. Quant. 38(3): 259–289, 2004).     

The Structure of the Log Odds-Ratios in Non-Independence and Symmetry Diagonal Models for Square Contingency Tables

This paper examines the structure of the interaction term when expressed as the log ofthe odds-ratios ij in the log-linear model formulation of non-independence and symmetry diagonalmodels applied to an I x I contingency table having ordinal classificatory variables. The class ofprincipal diagonal, diagonal band, full diagonal and diagonal-parameters symmetry models areexamined in the study. The general structure of Φ_ij is examined for each class of diagonal models.The 5 x 5 British Social Mobility data (Glass, 1954) will be employed as an example in this paper.The structure of the log odds-ratios are formulated in terms of the parameter estimates obtained from the application of SAS PROC GENMOD. Goodman in several of his papers on the subject has also derived some of these log odds ratios but our focus here is the structure of these odds, when viewed from the non-standard log-linear perspective (Lawal, 2001, 2002).     

Does authenticity exist in cultural theme parks? A case study of Millennium City Park in Henan,China

ABSTRACT

Authenticity has always been a salient concept in tourism studies. Most previous studies focused on cultural heritage sites while much less research was conducted on man-made attractions. Given the importance of authenticity in the tourism industry, this research investigates different authenticity concepts in a unique context: a Chinese cultural theme park. Millennium City Park is a typical cultural theme park in Kaifeng, Henan, China, and was chosen as the case study. This study identifies the perception of authenticity from the perspectives of both park managers and park visitors. It is found that visitors value authentic experience in the experience economy. Authenticity plays an important role in the tourism industry, in which activity-related authenticity is more important to visitors than object-related authenticity in cultural theme parks since visitors prefer more participation and involvement during their visits. It is suggested that park planners emphasize cultural elements in various products in cultural theme parks.     

Perceptual content analysis for city image: a case study of Hong Kong

This paper presents a case study investigating the most salient impressions and unique attractions of Hong Kong, perceived by government officials, inbound visitors and local residents. The study utilizes neural network analytical content analysis as a tool to understand the shared and disparate images and perceptions of the uniqueness of Hong Kong by quantifying the occurrence of open-ended self-reported textual answers by the respondents. The clustering of the answers and perceptual mapping confirms that the stakeholder groups think of Hong Kong as a conventional tourist destination and as a cosmopolitan metropolis. This strong stereotype, which displays an obvious knowledge gap between visitors and residents, as well as inter-group discrepancies, has created obstacles to innovating Hong Kong's image and branding.     

How a green city brand determines the willingness to stay in a city: the case of Hong Kong

This paper studies how biophysical green resources can become brand dimensions that affect the willingness of non-local people to stay in Hong Kong. Based on the Green (Resource) Brand Hexagon (GBH), the green brand attributes of Hong Kong were tested with two samples: inbound visitors (n = 396) and outsiders, most of whom had not visited Hong Kong (n = 235). The results show that visitors have more diversified determinants than outsiders, with safety, accessibility, and the aesthetic value of parks and landscapes in particular increasing respondents’ willingness to stay in Hong Kong. Outsiders perceive that a pleasant experience in physical spaces is primarily relevant to their willingness to stay in Hong Kong for seeking employment and education. However, green brand attributes play only a small part in the views of both respondent groups, indicating the presence of non-environmental factors in the decision to stay in a city.