The Official ACT Student website states you must do the following to get the most points on the ACT Science Test: “understand the information provided, examine critically the relationships between the information and the possible interpretation, and generalize from the information in order to draw conclusions or make predictions.”

A prediction is an inference you make based on the given information. You will ALWAYS need to understand the given information first, before you can use it as the basis for your prediction. Sometimes all you will need to do is to carefully interpret the data to answer the question, and sometimes you’ll need to extend the information given to you by the passage:

Based on Figure 2, the oxygen saturation of Individual 2 at an altitude of 7 miles would be closest to:

A   0%

B   30%

C   60%

D   90%

The altitude in the question, 7 miles, is 1 mile higher than the highest data point shown in Figure 2 so this means we will have to make our own prediction.  We can do this by extrapolating the line that would be formed by connecting the “Individual 2” data points. From 4 miles to 6 miles this line drops from approximately 80% to approximately 50% – a drop of 30% as the altitude increases by 2 miles.       Extending the line, a further increase of 1 mile (half of 2 miles) in altitude would result in a further drop of 15% (half of 30%) in saturation. The final saturation would equal 50% minus 15%, or 35%. This is closest to answer B, 30%.

This question asked you to make a prediction for a given variable based on extending a graph. Another question might ask you to make a prediction for an entirely new variable but based on the current trends:

According to

Figure 1 and Table 1, if a third protein had been present, with a molecular weight of 13,400 Daltons, its elution time would have been approximately:

A   21 minutes

B   22 minutes

C   23 minutes

D   24 minutes

The key phrase here “if a third protein had been present” indicates that we will need to make a prediction for an entirely new situation based on the info they’ve given me. The molecular weight of the protein (13,400) lies between the weights of the two proteins in Table 1 (12,000 and 15,000). The time required for it to travel through the column will therefore be between the time required for the first protein (24 minutes) and the second protein (22 minutes). The weight lies approximately midway between the weights of the two proteins in the table, so its elution time will be close to midway between 24 and 22 minutes. The best estimate is 23 minutes, or choice C.