provided in a control system is to allow manual override of remote installations, either by a serial communication. link, modem, radio or other type of interface. In these installation the field device may be manually controlled until a. problem is corrected or until maintenance personnel can visit the site.
â¢ Doctors want to know how much hearing damage results from loud music. â¢ Teachers want to know whether or not listening to classical music helps students perform better on tests. Statistical investigations are used every day for a variety of reasons.
Cross-sectional studies involve data collected at a defined time. They are often used to assess the prevalence of acute or chronic conditions, or to answer questions about the causes of disease or the results of intervention. They may also be described as censuses.