A sample of 40 general practicians (GPs) in Western Australia hospitals were surveyed and it was found that the average time they had spent with a patient was 18.2 minutes. Based on a large number of similar surveys, it was known that the standard deviation of time spent with a patient is 5.6 minutes. The critical value needed to construct the lower limit of a 95% confidence interval for the population mean time (in minutes) spent with a patient is_____________ (2 decimal places)