How to Work with Qualitative Data
In statistics, qualitative data divides a data set (the pool of data that you’ve gathered) into discrete chunks based on a specific attribute. You can then find information such as percentage amounts and mode. For example, in a class of students, qualitative data can include
Each child’s gender
His or her favorite color
Whether he or she owns at least one pet
How he or she gets to and from school
You can identify qualitative data by noticing that it links an attribute — that is, a quality — to each member of the data set. For example, four attributes of Emma are that she’s female, her favorite color is green, she owns a dog, and she walks to school.
Qualitative data usually divides a sample into discrete chunks. The following sample — which is purely fictional — uses 25 children in Sister Elena’s fifth grade class. For example, suppose all 25 children in Sister Elena’s class answer the three yes-or-no questions in the following list.
The students also answer the question What is your favorite color? with the results shown in the following list.
Even though the information that each child provided is non-numerical, you can handle it numerically by counting how many students made each response and working with these numbers.
Given this information, you can now make informed statements about the students in this class just by reading the charts. For instance,
Exactly 20 children have at least one brother or sister.
Nine children don’t take the bus to school.
Only one child’s favorite color is yellow.
How to find percentages with qualitative data
You can make more-sophisticated statistical statements about qualitative data by finding out the percentage of the sample that has a specific attribute. Here’s how you do so:
Write a statement that includes the number of members who share that attribute and the total number in the sample.
Suppose you want to know what percentage of students in Sister Elena’s class are only children. The chart tells you that 5 students have no siblings, and you know that 25 kids are in the class. So you can begin to answer this question as follows:
Five out of 25 children are only children.
Rewrite this statement, turning the numbers into a fraction:
In the example, 5/25 of the children are only children.
Turn the fraction into a percent.
You find that 5 ÷ 25 = 0.2, so 20% of the children are only children.
Similarly, suppose you want to find out what percentage of children take the bus to school. This time, the chart tells you that 16 children take the bus, so you can write this statement:
Sixteen out of 25 children take the bus to school.
Now rewrite the statement as follows:
16/25 of the children take the bus to school.
Finally, turn this fraction into a percent. When you find 16 ÷ 25, you get 0.64, or 64%:
64% of the children take the bus to school.
How to find the mode of a quantitative data set
The mode tells you the most popular answer to a statistical question. For example, in the above poll of Sister Elena’s class, the mode groups are children who
Have at least one brother or sister (20 students)
Own at least one pet (14 students)
Take the bus to school (16 students)
Chose blue as their favorite color (8 students)
When a question divides a data set into two parts (as with all yes-or-no questions), the mode group represents more than half of the data set. But when a question divides a data set into more than two parts, the mode doesn’t necessarily represent more than half of the data set.
For example, 14 children own at least one pet, and the other 11 children don’t own one. So the mode group — children who own a pet — is more than half the class. But 8 of the 25 children chose blue as their favorite color. So even though this is the mode group, fewer than half the class chose this color.