A scientist in Finland wants to discover if there is a relationship between the amount of sleep someone gets each night and his or her grades. Currently, there is only 6 hours of daylight in Finland. The scientist talks to 500 students from a local college as they exit a library in the evening. The results from the study show that there is a weak but noticeable correlation between sleep and grades in these students. A media outlet in New York finds the study and wants to share the findings. They write the headline: "Sleep better to get higher grades? It may not matter as much as you think." Is the conclusion in the headline justified?

Correlation is a statistical measure of mutual related movement in two variables. It denotes two variables move in same or opposite direction, their magnitude. Correlation coefficient lies between 0 & 1.

Positive correlation : Variables move in same direction - one increase, other variable increase & one variable decrease, other variable decrease. Correlation r is positive +
Negative correlation : Variables move in opposite direction - one variable increase, other variable decrease & one variable decrease, other variable increase. correlation r is negative -
Strong Correlation : Variables' movement are more interdependent. correlation r > 0.5
Negative Correlation : Variables' movement are less interdependent. correlation r is < 0.5

As, study shows that there is weak but noticeable (positive) correlation between sleep & grades : It states that high sleep implies high grades, low sleep implies low grades, but the rise or fall in grades, with rise or fall in sleep is very less. So, the headline denoting that 'sleeping better for higher grades doesn't matter much' aptly denotes the study results.