What makes a variable dependent, independent, or qualitative data?

Explanation:

An independent variable is a variable that is changed to ellicit an effect. Or it what is changed in an experiment. This makes it independent because it is not affected by changes because it is what will change.

A dependent variable is the variable that is not changed or manipulated intentionally. It is called dependent, because the change in this variable is "Dependent" on the changes done on the independent variable.

Let's take a simple scenario:

Adding sugar will make tea sweeter.

We have the variables amount of sugar and the taste of tea.

To test this, what will you change to see if it is true?

You will change the amount of sugar.

So in this case, the amount of sugar is the independent variable.

What then is affected by the change in the amount of sugar?

The taste of tea is what is affected.

So in this case, the taste of tea is the dependent variable, because it is dependent on the change in amount of sugar.

Now what is qualitative data?

Qualitative data is a type of data that is not quantifiable. Instead, they are descriptors. For example, in the scenario, sweetness is a qualitative data. It cannot be measured in numbers, but it is expressed as a description.

Another example would be satisfaction, pain, and the like. Any type of data that is obtained that is categorical is considered as qualitative data.  

it will increase due to the time span