The effect of correlation between demands on hierarchical forecasting

The forecasting needs for inventory control purposes are hierarchical. For SKUs in a product family or a SKU stored across different depot locations, forecasts can be made from the individual series’ history or derived top-down. Many discussions have been found in the literature, but it is not clear under what conditions one approach is better than the other. Correlation between demands has been identified as a very important factor to affect the performance of the two approaches, but there has been much confusion on whether positive or negative correlation. This paper summarises the conflicting discussions in the literature, argues that it is negative correlation that benefits the top-down or grouping approach, and quantifies the effect of correlation through simulation experiments

Investigation and Evaluation of COVID-19 Response by Purdue University of Fort Wayne in Welcoming Back Students

This research investigates the success of Purdue University, Fort Wayne’s Campus Kickoff event in the middle of the COVID-19 Pandemic and the planning to minimize the spread and infection. Researchers observed the attending student population, along with the presence of the virus on campus to determine the precautions effectiveness. Purdue University, Fort Wayne committed a normal approach while other campuses moved online. After examining the school’s infections before and after the Campus Kickoff event, we have discovered infection rates across campus proved there was no significant outbreak because of the event, meaning the prevention measures show to have been successful

Milk production in Finnsheep and Romanov breeds

The Finn, Romanov and several U.S. sheep breeds were machine milked to obtain information on several measures of milk production and milk composition. Data were obtained over at wo year to four year period utilizing 146 purebred ewe records and 165 crossbred ewe records. The level of milk production for a 130 day lactation period for the breeds evaluated was generally low compared to traditional European dairy breeds. The least-squares overall mean for milk yield was 68.8 liters. The Suffolk (80.5 liters) and the Rambouillet (75.3 liters) were superior. The Targhee, Dorset and Lincoln breeds followed in order for milk yield. The Finn (64.0 liters) and Romanov (39.1 liters) were lowest. Finn sired crossbred ewes had the highest level of milk production (84.4 liters) in a four breed diallel mating design of Finn, Dorset, Lincoln and Rambouillet breeds. A value of 15.4 % was found for heterosis in milk production

Formation of seasonal groups and application of seasonal indices

Estimating seasonal variations in demand is a challenging task faced by many organisations. There may be many stock-keeping units (SKUs) to forecast, but often data histories are short, with very few complete seasonal cycles. It has been suggested in the literature that group seasonal indices (GSI) methods should be used to take advantage of information on similar SKUs. This paper addresses two research questions: (1) how should groups be formed in order to use the GSI methods? and (2) when should the GSI methods and the individual seasonal indices (ISI) method be used? Theoretical results are presented, showing that seasonal grouping and forecasting may be unified, based on a Mean Square Error criterion, and K-means clustering. A heuristic K-means method is presented, which is competitive with the Average Linkage method. It offers a viable alternative to a company’s own grouping method or may be used with confidence if a company lacks a grouping method. The paper gives empirical findings that confirm earlier theoretical results that greater accuracy may be obtained by employing a rule that assigns the GSI method to some SKUs and the ISI method to the remainder

Norm Detachment: Unwillingness of Millennials to Negotiate

Although millennials seem aware of the need for negotiating, salaries paid to starting employees do not always reflect this. It is much more likely for a job candidate to accept an offer for employment without negotiation than it is for a job candidate to bargain for a higher salary. At one point in time bargaining for a higher salary was commonplace. However, due to unknown circumstances millennials seem to be unwilling to negotiate. Our results show that millennials do not negotiate during times viewed as appropriate and times where negotiating could reap substantial benefit. This raises certain questions as to why that may be. We have looked at numerous articles about the behavior of millennials and their skills in negotiating. The results of these articles showed that millennials may not negotiate due to embarrassment or lack of care, but we also found that millennials can be taught how to negotiate. Our research also shows that millennials tend to do things on impulse or for instant gratification

The connection between the host halo and the satellite galaxies of the Milky Way

Many properties of the Milky Way's dark matter halo, including its mass assembly history, concentration, and subhalo population, remain poorly constrained. We explore the connection between these properties of the Milky Way and its satellite galaxy population, especially the implication of the presence of the Magellanic Clouds for the properties of the Milky Way halo. Using a suite of high-resolution $N$-body simulations of Milky Way-mass halos with a fixed final Mvir ~ 10^{12.1}Msun, we find that the presence of Magellanic Cloud-like satellites strongly correlates with the assembly history, concentration, and subhalo population of the host halo, such that Milky Way-mass systems with Magellanic Clouds have lower concentration, more rapid recent accretion, and more massive subhalos than typical halos of the same mass. Using a flexible semi-analytic galaxy formation model that is tuned to reproduce the stellar mass function of the classical dwarf galaxies of the Milky Way with Markov-Chain Monte-Carlo, we show that adopting host halos with different mass-assembly histories and concentrations can lead to different best-fit models for galaxy-formation physics, especially for the strength of feedback. These biases arise because the presence of the Magellanic Clouds boosts the overall population of high-mass subhalos, thus requiring a different stellar-mass-to-halo-mass ratio to match the data. These biases also lead to significant differences in the mass--metallicity relation, the kinematics of low-mass satellites, the number counts of small satellites associated with the Magellanic Clouds, and the stellar mass of Milky Way itself. Observations of these galaxy properties can thus provide useful constraints on the properties of the Milky Way halo.Comment: 20 pages, 12 figures, accepted for publication in ApJ. A new section on the effect of host halo mass-assembly history on the central galaxy stellar mass is adde

Intended and Unintended Consequences of Prison Reform

Since the 1970s, U.S. federal courts have issued court orders condemning state prison crowding. However, the impact of these court orders on prison spending and prison conditions is theoretically ambiguous because it is unclear if these court orders are enforceable. We examine states' responses to court interventions and show that these interventions generate higher per inmate incarceration costs, lower inmate mortality rates, and a reduction in prisoners per capita. If states seek to minimize the cost of crime through deterrence, an increase in prison costs should lead states to shift resources from corrections to other means of deterring crime such as welfare and education spending. However, we find that court interventions, that are associated with higher corrections expenditures, lead to lower welfare expenditures. This suggests that the burden of increased correctional spending is borne by the poor. Furthermore, states do not increase welfare spending after their release from court order; making the reduction in welfare spending permanent. Thus, our results suggest that states do not respond to prison reform in the manner prescribed by the deterrence model. States' responses to prison reform are most consistent with the predictions in the empirical public finance literature that indicate stickiness in expenditure categories and that increases in spending in programs that affect the poor generate declines in expenditures in other program that are also targeted to the poor.

The importance of preventive feedback: inference from observations of the stellar masses and metallicities of Milky Way dwarf galaxies

Dwarf galaxies are known to have remarkably low star formation efficiency due to strong feedback. Adopting the dwarf galaxies of the Milky Way as a laboratory, we explore a flexible semi-analytic galaxy formation model to understand how the feedback processes shape the satellite galaxies of the Milky Way. Using Markov-Chain Monte-Carlo, we exhaustively search a large parameter space of the model and rigorously show that the general wisdom of strong outflows as the primary feedback mechanism cannot simultaneously explain the stellar mass function and the mass--metallicity relation of the Milky Way satellites. An extended model that assumes that a fraction of baryons is prevented from collapsing into low-mass halos in the first place can be accurately constrained to simultaneously reproduce those observations. The inference suggests that two different physical mechanisms are needed to explain the two different data sets. In particular, moderate outflows with weak halo mass dependence are needed to explain the mass--metallicity relation, and prevention of baryons falling into shallow gravitational potentials of low-mass halos (e.g. "pre-heating") is needed to explain the low stellar mass fraction for a given subhalo mass.Comment: 14 pages, 4 figures, accepted for publication in Ap