Students in a high school can choose to study Spanish or French as a foreign language. In a given academic year, 90% of the pupils choose Spanish and the rest choose French. 30% of the students who are learning Spanish are boys and 40% who are studying French are also boys. If a student was randomly selected from this academic year, what is the probability that it would be a girl?

#### Solution

` $$ \begin{aligned} P(Girl)&= P(Spanish)\times P(Girls|Spanish) + P(French)\times P(Girls|French)\\ &=0.9*0.7 + 0.1*0.6\\ & = 0.69 \end{aligned} $$ `

#### Further Reading

- Statistics
- Descriptive Statistics
- Probability Theory
- Probability Distribution
- Hypothesis Testing
- Confidence interval
- Sample size determination
- Non-parametric Tests
- Correlation Regression
- Statistics Calculators