• The World Happiness Report is a survey of the state of global happiness. It currently ranks 155 countries by their happiness levels.
• The hypothesis being tested in whether a country’s GDP per capita can influence its happiness score.

• Hypothesis testing is a method that uses testing to see if the data can prove a particular hypothesis.
• Null Hypothesis: There is no correlation between a country’s GDP per capita and its happiness score
  • If a country has a high GDP, they won’t have a high happiness score
• Alternative Hypothesis: There is a correlation between a country’s GDP per capita and its happiness score
  • If a country has a high GDP, they will have a high happiness score

## `geom_smooth()` using formula = 'y ~ x'

• Correlation coefficient formula: \(t = \frac{\bar{x} - \mu}{\frac{\sigma}{\sqrt{n}}}\)

library(ggplot2)
ggplot(happiness_data, aes(x = Economy..GDP.per.Capita., 
                           y = Happiness.Score)) +
  geom_point() +
  geom_smooth(method = "lm", se = FALSE) +
  labs(x = "GDP per Capita", 
       y = "Happiness Score", 
       title = "Relationship between GDP 
       per Capita and Happiness Score")

## `geom_smooth()` using formula = 'y ~ x'

• Based on the three plots in the slides and the correlation coefficient (0.78), we can say that both of these indicate a strong positive linear relationship between GDP and happiness scores. Therefore, we can say that having a high GDP per capita leads to higher happiness scores within a country.