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The following table represents data for emergency department visits. NOTE: . indicates missing value Visits Year 21 22 25 Q4 2014 1,613 1,282 2015 1,311 1,235 944 879 2016 1,385 966 1,516 975 2017 1,276 1,083 1,318 1,087 2018 1,242 1, 102 1,536 831 2015 1, 122 1,059 If the data were entered into MS Excel as shown below using dummy variables to identify the quarter in which the visits occurred: Emergency Visits Year Welto Q2 Q4 2014 1,613 2014 1,282 2015 1,311 2015 1,235 2015 944 2015 879 2016 1,385 2016 966 2016 1,516 2016 975 2017 1,276 2017 1,083 2017 1,318 2017 1,087 2018 1,242 2018 1, 102 2018 1,536 2018 831 2019 1,122 2019 1,059 Which quarter represents the base, or reference category