Positional Avarages

Breaking Down Student Spending: A Look Through Quartiles, Deciles & Percentiles

 

In an effort to understand how students spend money on campus, we conducted a survey focused on their weekly expenditure. With the data collected, we applied various statistical tools—not just averages, but also quartiles, deciles, and percentiles—to better interpret the spread and behavior of the data. These measures help reveal patterns that a simple average might miss, such as how spending varies across different groups of students.

University Survey Data For Student Total Expenditure

Quartile 

A quartile divides data into four equal parts.

• Q1 (First Quartile): 25% of the data lies below this point.
• Q2 (Second Quartile): This is the median (50% of the data below it).
• Q3 (Third Quartile): 75% of the data lies below this point.

 Decile

A decile divides the data into ten equal parts.

• For example, D1 marks the point below which 10% of data lies,
  D5 is the same as the 50th percentile or median,
  D9 marks 90% of the data.

 Percentile

A percentile splits data into 100 equal parts.

• For example, the 90th percentile (P90) means 90% of the data lies below that value.

Use: Often used in test scores, rankings, and performance comparisons.

By using quartiles, deciles, and percentiles, we gained a deeper understanding of student spending habits. For instance, the 90th percentile highlighted the top spenders, while the first quartile showed where the lighter spenders stood. These insights are vital for campus vendors, policymakers, or even students themselves, to better plan and respond to spending trends.