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# Data Organization and Interpretation for Praxis II ParaPro Test Prep Study Guide (page 3)

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Updated on Jul 5, 2011

### Line Graph

A line graph is a graph used to show a change over time. The line moves from left to right to show how the data changes over a time period. If a line is slanted up, it represents an increase, whereas a line sloping down represents a decrease. A flat line indicates no change.

In the line graph below, the number of delinquent payments is charted for the first quarter of the year. Each week, the number of customers with outstanding bills is added together and recorded.

There is an increase in delinquency for the first two weeks, and then the level is maintained for an additional two weeks. There is a steep decrease after week five (initially) until the ninth week, where it levels off again—but this time at 0. The 11th week shows a radical increase followed by a little jump up at week 12, and then a decrease at week 13. It is also interesting to see that the first and last weeks have identical values.

This line graph shows an obvious trend because the points go up as the line moves to the right. That means there is a positive trend. A question on the ParaPro Assessment may ask you to make a prediction based on the trend. Each year, the profits of the company go up by about \$3 million. Therefore, if you were asked to predict the profits of the company in 2010, you could add \$3 million to the profits in 2009. An appropriate prediction for the company's total profits in 2010, based on the trend in the graph, would be \$21 million.

### Mean, Median, and Mode

It is important to understand trends in data. To do that, look at where the center of the data lies. There are a number of ways to find the center of a set of data.

### Mean

Average usually refers to the arithmetic mean (usually just called the mean). To find the mean of a set of numbers, add all of the numbers together and divide by the quantity of numbers in the set.

average = (sum of set) ÷ (quantity of set)

Example

Find the average of 9, 4, 7, 6, and 4.

(Divide by 5 because there are five numbers in the set.) The mean, or average, of the set is 6.