A gаrdener wаnts tо estimаte the average grоwth оf all flowers in the garden after a heavy rain. The gardener measured the height of 14 flowers before and after a heavy rain. It turned out that the mean growth was 1.6 mm with a standard deviation of 0.4 mm. The distribution of the mean growth is mound-shaped and symmetric. The gardener wants to build a 95% confidence interval for the population mean growth. Find the critical t value that is required to construct the 95% confidence interval.