Bar charts are often used to compare how something changes over time or from one type of thing to another. Questions on the GED that test your ability to read a bar chart often you to estimate the values represented on the chart, since the exact numbers often aren’t provided on bar charts. For this reason you should be sure to look at all of the multiple choice answers and choose the one closest to what you estimate from the chart. Let’s look at an example.
If a question asked you what a teacher made in 2010 you will see that the top of the 2010 bar is not on one of the lines for every $5,000 increment. Instead you see that it is about halfway between $35,000 and $40,000. Now don’t worry too much because there won’t be a question that has $37,500 and $38,000 as two of the multiple choices. Instead one of these two will be a possible answer and the other possible choices won’t even be close.
However, it’s not likely that you will see a bar chart question that straight-forward on the GED. Instead you might be asked about a year in between two of the bars, like 1993, or totally outside of the chart, like 1980.
Finding a Value Between Two Bars
Let’s say you are asked to provide the teacher salary in 1993. You can see the salaries in 1990 and 1995. For 1990 it looks like it was $29,000 and for 1995 it was $35,000. Since 1993 is closer to 1995 than 1990, your answer should be a little closer to $35,000 than $29,000, so maybe $32,000. You can do a calculation to find a more precise answer. First find the difference between 35,000 and 29,0000, which is 6,000. Now 1993 is 3 out of the 5 years on the way between 1990 and 1995, so multiply 3/5 by 6,000, which is 3,600. Add that to 29,000, and the average salary in 1993 was 32,600.
Finding a Value Outside the Chart Range
You might be asked what the value is for a field outside a chart’s range. This will only happen if the chart shows a clear trend. Using the table above as an example, you might be asked what the average teacher salary was in 1980. You can see that from 1985 to 2005 there is a clear upward trend, and since the growth in the two dates we know closest to 1980, which are 1985 and 1990, is only about 2 or 3 thousand, we can reasonably assume that the growth from 1980 to 1985 was also slight. It looks like the salary in 1985 was $26,000 so we can guess the salary in 1980 was around $23,500.