For example, if a researcher wants to see how well different doses of a medication work, the dose is the independent variable. Suppose you want to see if studying more improves your test scores. The amount of time you spend studying is the independent variable.

Say a researcher is testing an allergy medication. Allergy relief after taking the dose is the dependent variable, or the outcome caused by taking the medicine.

The $3 per chore is a constant. Your parents set that in stone, and that number isn’t going to change. On the other hand, the number of chores you do and the total amount of money you earn aren’t constant. They’re variables that you want to measure. To set up an equation, use letters to represent the chores you do and the money you’ll earn. Let t represent the total amount of money you earn and n stand for the number of chores you do.

Notice that the amount of money you’ll earn depends on the number of chores to do. Since it depends on other variables, it’s the dependent variable.

Say an episode of your favorite TV show is 30 minutes. The total time in minutes (m) you’ll spend watching TV equals 30 times the number of episodes (e) you watch. That gives you the equation m=30e{\displaystyle m=30e}. If you watch 3 episodes, m=(30)(3)=90{\displaystyle m=(30)(3)=90}.

Say you want to know how much you’ll earn if you do 8 chores instead of 5. Plug 8 into n: t=(3)(8)=24{\displaystyle t=(3)(8)=24}. It’s the same principle as a researcher changing the dose of a medication from 2 mg to 4 mg to test its effects.

Say you sell apples and want to see how advertising affects your sales. The amount of money you spent in a month on advertising is the independent variable, or the factor that causes the effect you’re trying to understand. The number of apples you sold that month is the dependent variable.

Suppose you’re trying to see if advertising more increases the number of apples you sold. Divide the x-axis into units to measure your monthly advertising budget. If you’ve spent between $0 and $500 a month in the last year on advertising, draw 10 dashes along the x-axis. Label the left end of the line “$0. ” Then label each dash with a dollar amount in $50 increments ($50, $100, $150, and so on) until you’ve reached the last dash, or “$500. ”

Suppose your monthly apple sales have ranged between 60 and 250 over the last year. Draw 10 dashes across the y-axis, label the first “50,” and label the rest of the dashes in increments of 25 (50, 75, 100, and so on), until you’ve written 275 next to the last dash.

For instance, if you spent $350 on advertising last month, find the dash labeled “350” on the x-axis. If last month’s apple sales totaled 225, find the dash labeled “225” on the y-axis. Draw a dot at the point at the graph coordinate ($350, 225), then continue graphing points for the rest of your monthly numbers.

For example, say you’ve graphed your advertising expenses and monthly apple sales, and the dots are arranged in an upward sloped line. This means that your monthly sales were higher when you spent more on advertising.