***Apologies for cross-posting Dear colleagues, We would like to draw your attention to the upcoming submission deadline (*February 28, 2023*) for the 4th Mobile Apps and Sensors in Surveys (MASS) workshop in Manchester (UK) in June 22-23, 2023. For the 4th MASS workshop, we invite contributions that focus, among others, on the following methodological issues when using mobile apps, sensors, and wearables in surveys: Technical aspects of mobile apps, sensors, and wearables     Different ways to collect sensor, app, and wearable data     Building apps for Android and iOS     Data processing and storage      Study and app design     Look and feel of apps     Usability studies     Use of incentives     Giving feedback to respondents Implementation     Willingness to participate and consent     Methods to invite and communicate with study participants     Study length and study intensity     Legal, ethical, and privacy considerations     Data handling Quality of data from mobile apps, sensors, and wearables     Errors of non-representation (self-selection, coverage, and nonparticipation)     Measurement error (prevention, modeling, and correction)     Validity of measurements with mobile apps, sensors, and wearables Data analysis     Analysis of sensor data     Combining survey data with data from mobile apps, sensors, and wearables Please submit your abstract for the workshop to b.struminskaya@uu.nl by *February 28, 2023*. The abstract should contain a research question, data collection procedures (e.g., a description of the app), and results, if available. If results are not available yet, the abstract should outline the type of analyses that will be presented at the workshop. For more detailed information on MASS, we refer you to the MASS website: https://massworkshop.org/ Organizing committee Alexandru Cernat (University of Manchester) Bella Struminskaya (Utrecht University) Peter Lugtig Florian Keusch (University of Mannheim) Jan Karem Höhne (University of Duisburg-Essen)