A line of best fit can only be drawn if there is strong positive or negative correlation. The line of best fit does not have to go through the origin.

Sometimes we plot points that don’t make a perfect pattern or that have no values in between. This is called discrete data and we don’t connect the dots with a line. They don’t have data in between the points already given. A continuous graph has a line because there is data in between the points already given.

In line graphs, the line is created by connecting each individual data point to show local changes, in this way, the local change from point to point can be seen. This is done when it is important to be able to see the local change between pair of points.

There are basically two reasons for joining the points: (i) it makes it easier to see the trend or relationship between two variables; (ii) it may be important to calculate what is happening between points – a process known as interpolation – or beyond the points plotted – a process known as extrapolation.

It does need to be straight. Try to make it go through as many points as possible and have as many points above the line as below. It’s a line of best fit, so it should fit the shape of the gradient whether it be straight or curved.

However if you’re drawing a line graph (as you will often have to do in GCSE Biology to show trends over time) you can connect the dots. Line graphs are only used when both variables are quantitative.

The line graph consists of a horizontal x-axis and a vertical y-axis. Most line graphs only deal with positive number values, so these axes typically intersect near the bottom of the y-axis and the left end of the x-axis. Data points are plotted and connected by a line in a “dot-to-dot” fashion.

How to make a graph

1. Identify your independent and dependent variables.
2. Choose the correct type of graph by determining whether each variable is continuous or not.
3. Determine the values that are going to go on the X and Y axis.
4. Label the X and Y axis, including units.
5. Graph your data.

Drawing Scientific Graphs

1. Give your graph a descriptive title.
2. Ensure you have put your graph the right way around.
3. Determine the variable range.
4. Determine the scale factor of the graph.
5. Label the horizontal and vertical axes with units clearly.
6. Remove any outliers.
7. Draw a line of best fit.

Scale means the number used to represent one unit length of a bar. For example, the scale for the bar graph shown here is 1 unit length = 100 children.

A bar graph can be defined as a chart or a graphical representation of data, quantities or numbers using bars or strips. Bar graphs are used to compare and contrast numbers, frequencies or other measures of distinct categories of data.

Simple and double bar graphs can be obtained as: First of all draw a horizontal line and a vertical line. On the horizontal line we will write the names of students and on vertical line we will write scores of maths and hindi. The scale taken is 1 unit = 5 marks.

A double bar graph is used to display two sets of data on the same graph. For example, if you wanted to show the number of hours that students worked in one month compared to another month, we would use a double bar graph. The information in a double bar graph is related, and it compares one set of data to another.

Steps to draw the bar graph: (3) Write the name of the animals on the X-axis at equal distances. (4) The number of animals is taken on the Y-axis. (5) Write the scale in the top right hand corner i.e. 1 cm = 4 animals on the Y-axis. (6) Draw a bar of the appropriate height above the name of each animal on the X-axis.

A multiple bar graph shows the relationship between different values of data. Each data value is represented by a column in the graph. In a multiple bar graph, multiple data points for each category of data are shown with the addition of columns. The quantity or amount of data is listed along the vertical, or y, axis.

To create a multiple bar graph:

1. Draw the horizontal (x) and vertical (y) axis.
2. Give the graph a title.
3. Label the horizontal x axis.
4. Label the vertical y axis.
5. Look at the range in data and decide how the units on the vertical axis (y) should be labeled.

A bar chart can be categorized into two broad types, namely; horizontal and vertical bar charts. These groups are further subdivided into the various categories such as vertical stacked bar chart, horizontal grouped bar chart, and the like.

Deviation bar graphs are simply two bar charts aligned, where one of the charts runs right to left rather than left to right. The two charts report on the same categories but differ in terms of respondent group or some other variable.

Error bars are graphical representations of the variability of data and used on graphs to indicate the error or uncertainty in a reported measurement. They give a general idea of how precise a measurement is, or conversely, how far from the reported value the true (error free) value might be.

A graph that visually displays data using vertical bars going up from the bottom, whose lengths are proportional to quantities they represent. It can be used when one axis cannot have a numerical scale.

The title of the horizontal bar graph tells about the data being represented by the graph. The vertical axis represents the data categories. The horizontal axis represents the values corresponding to each data value.

When developing bar graphs, draw a vertical or horizontal bar for each category or value. The height or length of the bar will represent the number of units or observations in that category (frequency) or simply the value of the variable. Select an arbitrary but consistent width for each bar as well.