While learning analytics (LA) practices have been shown to be practical and effective, most of them require a huge amount of data and effort. This paper reports a case study which demonstrates the feasibility of practising LA at a low cost for instructors to identify at-risk students in an undergraduate business quantitative methods course. Instead of using tracking data from a learning management system as predictive variables, this study utilised clicker responses as formative assessments, together with student demographic data and summative assessments. This LA practice makes use of free cloud services, Google Forms and Google Sheets in particular for collecting and analysing clicker data. Despite a small dataset being used, the LA implementation was effective in identifying at-risk students at an early stage. A systematic proactive advising approach is proposed as an intervention strategy based on students' at-risk probability estimated by a prediction model. The result shows that the intervention success rate increases correspondingly with the number of interventions and the intervention effects on peer groups are far more successful than on individual students. Overall, the students' pass rate in the study was 7% higher than that for the whole course. Practical recommendations and concerns about using linear regression and logistic regression for classification are also discussed.