11.01 Line plots with fourths and eighths

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Can you read information from a picture graph?

 

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A line plot is similar to a picture graph, but using dots rather than images to show the number of values. They are also usually drawn with the dots stacked vertically, while picture graphs are often shown horizontally.

Let's look at an example. A set of measurements (in inches) have been taken, with the results recorded in the table below:

$4$4	$5\frac{1}{2}$512​	$5\frac{1}{4}$514​	$4\frac{1}{2}$412​
$5$5	$3\frac{1}{2}$312​	$6\frac{1}{2}$612​	$5\frac{1}{4}$514​
$4\frac{1}{2}$412​	$5\frac{1}{4}$514​	$4$4	$5\frac{1}{4}$514​
$5$5	$4\frac{1}{4}$414​	$5\frac{1}{4}$514​	$4$4

To make a line plot, we start by counting up the number of times each measurement appears. For this table, we have:

• $1$1 measurement of $3\frac{1}{2}$312​
• $3$3 measurements of $4$4
• $1$1 measurement of $4\frac{1}{4}$414​
• $2$2 measurements of $4\frac{1}{2}$412​
• $2$2 measurements of $5$5
• $5$5 measurements of $5\frac{1}{4}$514​
• $1$1 measurement of $5\frac{1}{2}$512​
• $1$1 measurement of $6\frac{1}{2}$612​

We can now plot the number of dots at each value on the line plot:

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Question 1

 

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We can also use line plots to more easily understand key features of a data set. For instance, from a line plot we can clearly see which value is the most common by looking at which value has the most dots. We can also see the largest and smallest values in the data set.

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Question 2