Are Delayed Issues Harder to Resolve? Revisiting Cost-to-Fix of Defects throughout the Lifecycle

Many practitioners and academics believe in a delayed issue effect (DIE); i.e. the longer an issue lingers in the system, the more effort it requires to resolve. This belief is often used to justify major investments in new development processes that promise to retire more issues sooner. This paper tests for the delayed issue effect in 171 software projects conducted around the world in the period from 2006--2014. To the best of our knowledge, this is the largest study yet published on this effect. We found no evidence for the delayed issue effect; i.e. the effort to resolve issues in a later phase was not consistently or substantially greater than when issues were resolved soon after their introduction. This paper documents the above study and explores reasons for this mismatch between this common rule of thumb and empirical data. In summary, DIE is not some constant across all projects. Rather, DIE might be an historical relic that occurs intermittently only in certain kinds of projects. This is a significant result since it predicts that new development processes that promise to faster retire more issues will not have a guaranteed return on investment (depending on the context where applied), and that a long-held truth in software engineering should not be considered a global truism.Comment: 31 pages. Accepted with minor revisions to Journal of Empirical Software Engineering. Keywords: software economics, phase delay, cost to fi

Shifting the Tide: Transit-Oriented Development and Active Transportation Planning in Los Angeles

Los Angeles (LA) has the reputation of an auto dependent city. Although the region is served by a robust public transportation system, the majority of the population commutes by automobile and has developed in sprawling manner leading to poor air quality, traffic congestion and unsafe streets. Despite this, in recent years, the LA region has made significant headway in reversing sprawl and automobile use. This has included encouraging greater land use densities around transit stations, coupled with investments to active transportation systems. This article presents an overview of the historical context of automobile dependency in Los Angeles, the current transit-oriented development strategies underway, and the planning and implementation of Complete Street strategies. It uses this narrative to illustrate how the city is using these strategies to reduce greenhouse gas emissions and the impacts of climate change

Forrest B. Fordham Letter

A letter sent by Forrest B. Fordham, pastor of Holmesburg Baptist Church, of Philadelphia, Pennsylvania on December 30, 1942 to the First Christian Church of Morehead, Kentucky.https://scholarworks.moreheadstate.edu/mfcc_ww2_letters/1099/thumbnail.jp

Infrared and visible photometry of the gravitational lens systems 2237 + 030

As part of a program of high spatial resolution imaging of gravitationally lensed sources in the visible and IR, images of 2237 + 030 were obtained in the Gunn r and infrared J, H, K, and 3.3 micron filters. The results of the photometry of the four bright quasar components provide evidence of extinction through the lens and a determination of the extinction law in the galaxy is made. The energy distribution shows evidence of a sharp decrease of the spectral index at wavelengths longer than a rest wavelength of 1 micron. Assuming that microlensing amplification in the IR is of similar strength as in the visible, the data constrain the suggested microlensing event of August-September 1988 to a time scale of 100 days

Site-Specific Risk Factors for Ray Blight in Tasmanian Pyrethrum Fields

Ray blight of pyrethrum (Tanacetum cinerariifolium), caused by Phoma ligulicola var. inoxydablis, can cause defoliation and reductions of crop growth and pyrethrin yield. Logistic regression was used to model relationships among edaphic factors and interpolated weather variables associated with severe disease outbreaks (i.e., defoliation severity ≥40%). A model for September defoliation severity included a variable for the product of number of days with rain of at least 0.1 mm and a moving average of maximum temperatures in the last 14 days, which correctly classified (accuracy) the disease severity class for 64.8% of data sets. The percentage of data sets where disease severity was correctly classified as at least 40% defoliation severity (sensitivity) or below 40% defoliation severity (specificity) were 55.8 and 71%, respectively. A model for October defoliation severity included the number of days with at least 1 mm of rain in the past 14 days, stem height in September, and the product of the number of days with at least 10 mm of rain in the last 30 days and September defoliation severity. Accuracy, sensitivity, and specificity were 72.6, 73.6, and 71.4%, respectively. Youden\u27s index identified predictive thresholds of 0.25 and 0.57 for the September and October models, respectively. When economic considerations of the costs of false positive and false negative decisions and disease prevalence were integrated into receiver operating characteristic (ROC) curves for the October model, the optimal predictive threshold to minimize average management costs was 0 for values of disease prevalence greater than 0.2 due to the high cost of false negative predictions. ROC curve analysis indicated that management of the disease should be routine when disease prevalence is greater than 0.2. The models developed in this research are the first steps toward identifying and weighting site and weather disease risk variables to develop a decision-support aid for the management of ray blight of pyrethrum