Your variables are the two things that have been measured. You need to determine which axis you want each variable to lie; the general rule is that the independent variable, or the factor you control lies on the x-axis, whereas whatever you measure in relation to that is the dependent variable.









For example, if you are measuring how changing the amount of water fed to a sunflower plant affects growth, you would control how much water you give each sunflower plant and measure each plant’s growth after a fixed amount of time. Because the amount of water is controlled, the amount of water given each day would be recorded on the x-axis. It is understood that you expect plant growth to be dependent on how much water you give; therefore, it is dependent on the independent variable, and would be recorded on the y-axis.;
, Each data point has two numbers: the x-value and the y-value. These come in pairs and create a link between the two variables.









For example, if a plant that is watered 2 cups of water a day grows 6 inches (15.2 cm) in three weeks, its x-value is 2 (because it represents the variable that is controlled: water) and its y-value is 6 (because that is the variable that is measured: plant growth).
 This line does not necessarily have to go right through each point as long as it the curve is as smooth as possible and runs very close to as many points as possible.









This line represents the relationship between your two variables. For example, in the case of watering plants, giving too little water will completely dry out your plant and keep it from growing, but giving too much water will drown the plant and make it rot. Therefore, growth is very low for very low or very high quantities of water, and highest when the quantity of water is somewhere in between. The amount of water that causes the most growth is the highest point on the line

, The slope is how much the y-value increases when the x-value increases by 1.









On a straight line, the slope is constant. This is because the line does not ever get any steeper or flatter. As x increases, y increases by a constant amount, creating a straight line.
On a flat, horizontal line, the slope is 0. This is because no matter how x changes, the change in y is always zero.
On a vertical line, the slope is undefined. This is because you can’t measure how y changes with x because x never changes.
On a curved line, the slope is not constant. This is because the line changes in steepness as you go across; one unit of change in the x-axis does not always create the same change in the y-axis.
On a line with equation y=mx+b, the slope is m. This is because when x changes, y increases or decreases by the m multiplied by however much x changes. So, if x increases by 1, y increases by m.
 This is the value at which the line crosses the y-axis.









Note that every point on the y-axis has an x-value of 0. So, the y-intercept generally refers to the y-value at which the line crosses the y-axis.
On a line with equation y=mx+b, the y-intercept is b and lies at point (0,b). This can be shown by plugging in 0 for x.

y = m*0 + b = b


You can find the y-intercept for any equation with variables x and y by simply plugging in x=0 and solving for y.
Take your data and analyze your variables.
Plot each point.
Plot all your points and draw a line of best fit.This is a smooth line or curve that follows the dots as best as possible without making sharp corners.
Figure out the slope of the line.
Find the y-intercept.
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