Post-admission language tests tend to have a restricted range of proficiency levels among test-takers due to considerations made during the admission selection process.Although range restriction can present challenges...Post-admission language tests tend to have a restricted range of proficiency levels among test-takers due to considerations made during the admission selection process.Although range restriction can present challenges for proficiency-focused assessment,it can also bring opportunities to zoom in on fine-grained performance profiles of test-takers.This study reports on the validation of a profile-based rating scale for an ESL writing placement test in a US university.The profile-based rating scale was created by employing a three-staged,hybrid scale development approach,to provide not only accurate placement decisions but also fine-grained diagnostic information regarding ESL students’writing performance profiles.The scale strikes a balance between argument development and lexico-grammar,to better account for the range of writing performances among test-takers.To gather validity evidence for the profile-based rating scale,this study employs a sequential,mixed-methods approach to examine the quality of test-taker performances across profiles and rater perceptions on the scale.Nine certified raters were recruited to conduct independent evaluations of lexicogrammar and argumentation on a sample of 150 test-taker performances.These evaluations were subjected to many-facet Rasch measurement analysis to examine the differences across writing performance profiles included in the rating scale.Next,semi-structured,follow-up interviews were conducted with the raters,to complement the quantitative findings on the usability and effectiveness of the scale.The findings provide supportive evidence for the validity of the profile-based rating scale.I argue that by focusing on performance profiles,post-admission language tests can strengthen the alignment across curriculum,instruction,and assessment in ESL writing programs.展开更多
文摘Post-admission language tests tend to have a restricted range of proficiency levels among test-takers due to considerations made during the admission selection process.Although range restriction can present challenges for proficiency-focused assessment,it can also bring opportunities to zoom in on fine-grained performance profiles of test-takers.This study reports on the validation of a profile-based rating scale for an ESL writing placement test in a US university.The profile-based rating scale was created by employing a three-staged,hybrid scale development approach,to provide not only accurate placement decisions but also fine-grained diagnostic information regarding ESL students’writing performance profiles.The scale strikes a balance between argument development and lexico-grammar,to better account for the range of writing performances among test-takers.To gather validity evidence for the profile-based rating scale,this study employs a sequential,mixed-methods approach to examine the quality of test-taker performances across profiles and rater perceptions on the scale.Nine certified raters were recruited to conduct independent evaluations of lexicogrammar and argumentation on a sample of 150 test-taker performances.These evaluations were subjected to many-facet Rasch measurement analysis to examine the differences across writing performance profiles included in the rating scale.Next,semi-structured,follow-up interviews were conducted with the raters,to complement the quantitative findings on the usability and effectiveness of the scale.The findings provide supportive evidence for the validity of the profile-based rating scale.I argue that by focusing on performance profiles,post-admission language tests can strengthen the alignment across curriculum,instruction,and assessment in ESL writing programs.
文摘北斗卫星导航系统可提供(radio determination satellite service,RDSS)短报文通信服务是其独特之处.为适应北斗RDSS短报文通信收发机制,设计了一种可应用于北斗有源天线的自适应发射机电路.提出并验证了使用分段、低成本的线性放大器代替对数放大器,来实现环路控制电路(voltage control amplifier,VCA);通过在传统北斗有源天线发射链路前端增加自动增益控制电路(automatic gain control,AGC)模组,实现了有源天线在0~30 m对不同射频线缆材质、长度造成损耗的自动适应,从而保证了北斗短报文通信设备在天线端的一致性、可靠性与易用性.
