Design

Design

When scientists create experiments, many factors are considered to ensure the accuracy of the experiment. Scientists must choose an independent variable and dependent variable and then ensure that every other potential variable is controlled. They must then make sure they are using the proper equipment to obtain accurate results, and decide on units of measurement. Sometimes, scientists may conduct more than one experiment to see how different variables affect the results. 

On the ACT Science Test, you will be given passages that present the procedure and results of different scientific experiments. Design questions will test you on your understanding of the setup of these experiments, including the variables, controls, and measurements.

Understanding the Passage

Below is a sample passage from the ACT Science test that features Design questions. It is important to understand the information presented in the passage before attempting to answer the questions.

Answering the Questions

Now that you have read over the passage, we can look at the Design questions.

Question 1

This question is testing your understanding of how the experiment is set up. We are trying to determine which two sets of seeds were under the same conditions before being added to the petri dishes.

In Study 1, all of the seeds were stored at 5℃ for different numbers of weeks before being added to the petri dishes.

Table 1 shows the number of seeds that germinated at different germination temperatures, depending on the number of weeks they were stored (known as the storage period).

Note that the germination temperature is different than the storage temperature. The germination temperature is the temperature the seeds are exposed to in the petri dishes, while the storage temperature is the temperature the seeds were stored at prior to being added to the petri dishes.

While the seeds in Study 1 were stored for various weeks, in Study 2 the seeds were stored at various temperatures for a constant 10 weeks.

Table 2 shows the number of seeds that germinated at different germination temperatures, depending on their storage temperature, while Table 1 shows the number of seeds that germinated at different germination temperatures depending on their storage period.

Since all the seeds from Study 1 had a storage temperature of 5℃, and all the seeds from Study 2 had a storage period of 10 weeks, the seeds from Study 1 with a storage period of 10 weeks and the seeds from Study 2 with a storage temperature of 5℃ had the same storage conditions.

Therefore, the answer is G.

Question 2

This question is asking how the designs of Study 1 and Study 2 differ.

By answering the previous question, we saw that Study 1 varied the storage period and kept the storage temperature constant, while Study 2 varied the storage temperature and kept the storage period constant. In both experiments, the germination temperature was varied.

We can see that in Study 2, the storage period was held constant at 10 weeks. Therefore, the answer is F.