Roughly speaking, we say that two variables are positively correlated if an increase in value of the first variable causes an increase in the value of the second variable and a decrease in the value of the first variable causes a corresponding decrease in the value of the second variable. We now list out 5 real-life examples of positive correlation among two variables.
1. Height and Shoe Size
It is an empirical fact that the height and shoe size of individuals are positively correlated to each other. A taller person will tend to have a larger shoe size compared to a shorter person. This is also observed in the course of a person’s life where, as a child grows taller their shoe size increases.
2. Time spent studying and Marks Obtained in Exam
It is clear that students who spend more time studying for an exam will have a comparatively better performance than those students who spend less time studying. This means that there is a positive correlation between how hard a student works to prepare for the exam and the final results obtained by the student.
3. GDP of a country and Average Lifespan of Citizens
It is an established fact that the citizens of richer countries generally have a greater average lifespan compared to the citizens of poorer countries. The GDP serves as a rough measure of how wealthy a country is. For example in the year 2020, the average lifespan of citizens of Japan was 84.3 years whereas, the average lifespan of citizens of Somalia was 56.5 years.
4. Income and Expenditure
It has been observed that the increase in the income of an individual is positively correlated with the expenditure of the individual. This means that as the income of a person increases there is a corresponding increase in the monthly expenditure of the individual. This can be explained by the fact that having a greater amount of disposable income lead to a higher degree of spending on leisure activities. Also, a salaried person’s income generally increases with age so the increase in expenditure may be caused due to marriage, children, etc.
5. Heights of Parents and Heights of Children
On average, the offspring of taller individuals tend to be taller. So if a person’s parents are tall it is much more likely that the child will be taller as well. The heights of parents and offspring are thus positively correlated because of genetic factors.