Suppose you believe that a specific type of plant will grow better in soil than in sand. You want to run an experiment to test your hypothesis.

Question

I could buy a sunflower seed packet from grocery outlet. I open the packet finding 7 sunflower seeds inside. I plant 3 sunflower seeds in 3 pots of soil and plant the other 3 sunflower seeds in 3 pots of sand. I also will water each plant every day and ensure each plant has the same amount of sunlight. Then I can measure the height of the sunflowers after one month.
What are the treatments in your experiment?
The treatment would be the soil or sand the plants grow in.

What is the response variable in your experiment?

The response variable in my experiment is the amount of plant growth

Where in your experiment would random selection occur?

Where in your experiment would random assignment occur?

Answer 1

In your experiment, random selection and random assignment are important concepts to consider for ensuring that your results are valid and reliable.

Random Selection:

In this experiment, random selection would occur if you were to randomly choose the sunflower seeds from a larger population (e.g., a larger packet or a variety of sunflower seeds) to ensure that the seeds you are using represent a wider group of seeds. However, since you mentioned that you only have 7 seeds in total, random selection is not applicable, as you're working with a limited sample size.

Random Assignment:

Random assignment refers to how you assign the sunflower seeds to each treatment group (soil vs. sand). To implement random assignment in your experiment, you could randomly assign which of your 3 pots receive soil and which receive sand. For example, after labeling your pots as "soill" and "sand," you might use a random number generator or draw lots to decide which seeds will go into which type of medium. This step is crucial for controlling any bias and ensuring that each treatment group is comparable.

To summarize:

• Random Selection: Not applicable in your current experiment due to the limited number of seeds.
• Random Assignment: Would occur when deciding which sunflower seeds go into the pots with soil and which go into the pots with sand, using a random method to assign the seeds to each treatment group.