title: The sense and non-sense of holdout sample validation in the presence of endogeneity

authors: Ebbes, Peter

subjects: model validation

abstract: Market response models based on field-generated data need to address potential endogeneity in the regressors to obtain consistent parameter estimates. Another requirement is that market response models predict well in a holdout sample. With both requirements combined, it may seem reasonable to subject an endogeneity-corrected model to a holdout prediction task, and this is quite common in the academic marketing literature. One may be inclined to expect that the consistent parameter estimates obtained via instrumental variables (IV) estimation predict better than the biased ordinary least squares (OLS) estimates. This paper shows that this expectation is incorrect. That is, if the holdout sample is similar to the estimation sample so that the regressors are endogenous in both samples, holdout sample validation favors regression estimates that are not corrected for endogeneity (i.e., OLS) over estimates that are corrected for endogeneity (i.e., IV estimation). We also discuss ways in which holdout samples may be used sensibly in the presence of endogeneity. A key takeaway is that if consistent parameter estimates are the primary model objective, the model should be validated with an exogenous (rather than endogenous) holdout sample.

text: The sense and non-sense of holdout sample validation in the presence of endogeneity Market response models based on field-generated data need to address potential endogeneity in the regressors to obtain consistent parameter estimates. Another requirement is that market response models predict well in a holdout sample. With both requirements combined, it may seem reasonable to subject an endogeneity-corrected model to a holdout prediction task, and this is quite common in the academic marketing literature. One may be inclined to expect that the consistent parameter estimates obtained via instrumental variables (IV) estimation predict better than the biased ordinary least squares (OLS) estimates. This paper shows that this expectation is incorrect. That is, if the holdout sample is similar to the estimation sample so that the regressors are endogenous in both samples, holdout sample validation favors regression estimates that are not corrected for endogeneity (i.e., OLS) over estimates that are corrected for endogeneity (i.e., IV estimation). We also discuss ways in which holdout samples may be used sensibly in the presence of endogeneity. A key takeaway is that if consistent parameter estimates are the primary model objective, the model should be validated with an exogenous (rather than endogenous) holdout sample.

year: 2011

title: Carbon emissions efficiency and economics of combined heat and power in New Zealand

authors: Atkins, Martin John

abstract: Combined Heat and Power (CHP) or cogeneration, is a common and often cost effective method to maximise the efficiency and utilisation of fossil fuels. Greenhouse Gas (GHG) emissions from the electricity generated using CHP is also an important factor to consider, especially within the framework of emissions reduction and uptake of renewable generation. This paper will present a detailed analysis of the economics of industrial CHP within New Zealand and examine the potential of CHP to contribute to GHG emissions reduction. An emissions factor from electricity generation using CHP is defined based on the marginal efficiency of electricity generation. The economics of CHP in New Zealand can be favourable under certain conditions although the emissions of generation using fossil fuels in all cases was higher than grid purchased electricity, due to high levels of renewable generation. A reduction in emissions can occur in countries that have medium to high Grid Emissions Factors (GEF) such as the US, UK, Australia, India, and China. Countries with GEF less than around 0.2 t CO2-eq /MW el would need to utilise biomass to achieve large emissions reductions using CHP.

text: Carbon emissions efficiency and economics of combined heat and power in New Zealand Combined Heat and Power (CHP) or cogeneration, is a common and often cost effective method to maximise the efficiency and utilisation of fossil fuels. Greenhouse Gas (GHG) emissions from the electricity generated using CHP is also an important factor to consider, especially within the framework of emissions reduction and uptake of renewable generation. This paper will present a detailed analysis of the economics of industrial CHP within New Zealand and examine the potential of CHP to contribute to GHG emissions reduction. An emissions factor from electricity generation using CHP is defined based on the marginal efficiency of electricity generation. The economics of CHP in New Zealand can be favourable under certain conditions although the emissions of generation using fossil fuels in all cases was higher than grid purchased electricity, due to high levels of renewable generation. A reduction in emissions can occur in countries that have medium to high Grid Emissions Factors (GEF) such as the US, UK, Australia, India, and China. Countries with GEF less than around 0.2 t CO2-eq /MW el would need to utilise biomass to achieve large emissions reductions using CHP.

year: 2017

title: Desirable attributes for medical graduates: The health aspirations and needs of Maaori living in Te Rohe Pootae

authors: Maikuku, Victoria Louisa Wikitoria

abstract: Health disparities for Maaori, the tangata whenua of Aotearoa New Zealand, are prevalent when compared to the health of European New Zealanders, and even more so in remote and rural communities where access to health-care services is limited. Moreover, Maaori are underrepresented in the medical workforce in which there is a serious and escalating shortage of doctors and nurses.

In the context of the University of Waikato’s proposal to establish a Graduate Entry Medical School, Te Huataki Waiora School of Health has identified the need for a collaborative approach to ‘growing’ a fit-for-purpose health workforce with the skills and commitment to care for and work with Maaori (and Pacific peoples) living in remote and rural communities. This study thus explores the health perspectives, needs, and aspirations of Maaori living in and around the King Country rural service towns of Te Kuiti and OOtorohanga. Conducted by a Ngaati Maniapoto tribal member, the location for the study is known by Maaori as Te Rohe Pootae - the lands of Rereahu/Maniapoto, to which the Waikato people sort refuge after the invasion and confiscation of their lands in the 1860s. The perspectives, needs, and aspirations of Pacific peoples living in these communities have been explored in a ‘sister’ Masters study conducted by Janina Galewski.

The present exploratory study incorporates a co-design research process underpinned by an Indigenous health framework with Kaupapa Maaori values. Kanohi ki te kanohi (face to face) semi-structured interviews were conducted with 30 community members, 11 males and 19 females aged 18 years and over. The data analysis included a combination of values, verses and holistic, and provisional coding methods (focused, thematic, descriptive) (Saldana, 2021).

The findings reveal that these community members view themselves as either rural or remote based on distance, access to services, and geographic isolation, but not population numbers. In terms of services, they want a mobile health workforce including clinics, carers, doctors, nurses; mental health workers who are equipped with the resources and time needed to reach and serve their patients; and better access to dialysis and related services. The research also identifies three healthcare strategies. When ill or injured, one-third of the group go directly to their GP; one-third try other things before seeking medical assistance, including going home to their parents and/or to their marae for comfort and advice, ‘going bush’ to (re)connect with nature, and forms of pure (cleansing rituals); and although the remaining third are registered with medical centres they do everything they can to avoid seeing a doctor at all. Instead, they rely on rongoaa and other ‘complementary and alternative’ treatments such as physiotherapists, chiropractors, osteopaths, and other healers. 

Adopting and adapting a table created by Woolley et al. (2013), the findings also revealed three sets of desirable attributes for medical graduates (and other healthcare professionals): Skill-based attributes include quality care and communication skills, knowledge-based attributes include medical knowledge and culturally appropriate knowledge, while attitude-based attributes include personality and community engagement. This framework can be used to inform a medical education curriculum, with a specific emphasis on the health needs and aspirations of Maaori living in rural and remote communities.

text: Desirable attributes for medical graduates: The health aspirations and needs of Maaori living in Te Rohe Pootae Health disparities for Maaori, the tangata whenua of Aotearoa New Zealand, are prevalent when compared to the health of European New Zealanders, and even more so in remote and rural communities where access to health-care services is limited. Moreover, Maaori are underrepresented in the medical workforce in which there is a serious and escalating shortage of doctors and nurses.

In the context of the University of Waikato’s proposal to establish a Graduate Entry Medical School, Te Huataki Waiora School of Health has identified the need for a collaborative approach to ‘growing’ a fit-for-purpose health workforce with the skills and commitment to care for and work with Maaori (and Pacific peoples) living in remote and rural communities. This study thus explores the health perspectives, needs, and aspirations of Maaori living in and around the King Country rural service towns of Te Kuiti and OOtorohanga. Conducted by a Ngaati Maniapoto tribal member, the location for the study is known by Maaori as Te Rohe Pootae - the lands of Rereahu/Maniapoto, to which the Waikato people sort refuge after the invasion and confiscation of their lands in the 1860s. The perspectives, needs, and aspirations of Pacific peoples living in these communities have been explored in a ‘sister’ Masters study conducted by Janina Galewski.

The present exploratory study incorporates a co-design research process underpinned by an Indigenous health framework with Kaupapa Maaori values. Kanohi ki te kanohi (face to face) semi-structured interviews were conducted with 30 community members, 11 males and 19 females aged 18 years and over. The data analysis included a combination of values, verses and holistic, and provisional coding methods (focused, thematic, descriptive) (Saldana, 2021).

The findings reveal that these community members view themselves as either rural or remote based on distance, access to services, and geographic isolation, but not population numbers. In terms of services, they want a mobile health workforce including clinics, carers, doctors, nurses; mental health workers who are equipped with the resources and time needed to reach and serve their patients; and better access to dialysis and related services. The research also identifies three healthcare strategies. When ill or injured, one-third of the group go directly to their GP; one-third try other things before seeking medical assistance, including going home to their parents and/or to their marae for comfort and advice, ‘going bush’ to (re)connect with nature, and forms of pure (cleansing rituals); and although the remaining third are registered with medical centres they do everything they can to avoid seeing a doctor at all. Instead, they rely on rongoaa and other ‘complementary and alternative’ treatments such as physiotherapists, chiropractors, osteopaths, and other healers. 

Adopting and adapting a table created by Woolley et al. (2013), the findings also revealed three sets of desirable attributes for medical graduates (and other healthcare professionals): Skill-based attributes include quality care and communication skills, knowledge-based attributes include medical knowledge and culturally appropriate knowledge, while attitude-based attributes include personality and community engagement. This framework can be used to inform a medical education curriculum, with a specific emphasis on the health needs and aspirations of Maaori living in rural and remote communities.

year: 2022