1. A researcher wanted to check whether the BMI of Canadian adults with obesity has increased in 2009 compared to 2005. He used Health Canada data. A randomly selected 20 Canadian adults from 2005 data gave a mean of 26.4 and a standard deviation of 1.3; A randomly selected 30 Canadian adults from 2009 data gave a mean of 27.1 with a standard deviation of 1.1. BMI is normally distributed in each year with the same variance. He wants to develop a 95% confidence interval for the change in BMI. Let population1 be 2005 data and population2 be 2009 data. Write down the critical value