The mean life satisfaction for 136 countries around the world in 2018 (on a scale from 0 – 10) was 5.5 with a standard deviation of 1.2. A sample of 50 countries taken in 2020 showed a mean of 5.2. Is...

The mean life satisfaction for 136 countries around the world in 2018 (on a scale from 0 – 10) was 5.5 with a standard deviation of 1.2. A sample of 50 countries taken in 2020 showed a mean of 5.2. Is the 2020 sample significantly lower than the mean happiness in 2018? Conduct the appropriate hypothesis test using