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The experimental units, explanatory and response variables, and treatments must all be identified.

The treatments are randomly assigned to all of the experimental units in a completely randomized design.

In a double-blind experiment, neither the subjects nor the people who interact with them and assess the response variable are aware of the treatment they received.

Observational research looks at people and assesses factors of interest without trying to affect their responses.

Individuals are purposely subjected to a treatment in order to measure their responses in an experiment.

An experiment tests the ability of pine trees to grow in the shade. According to studies, pine seedlings should be planted in full sun, with the sun reducing them to $25\%$ and the light reducing them to$5\%$ under natural conditions. Identify the topics and variables. Treatments and response variables are described in the method.

The following questions are asked in this experiment:

Because the research is focused on the capacity of pine trees, the pine forest in Arizona's dry forest is considered experimental.

Light is the most important factor in the experiments because the method is carried out under the effect of light.

Treatments: The light is divided into three equal halves.

1) Full sun: pine seedlings receive full light.

2) Light intensity was reduced to $25\%$ of average: pine seedlings received $25\%$ less light than usual.

3) Light reduced to $5\%$ natural: Pine seedlings receive $5\%$ less light than typical.

In the experiment, three treatments are described as follows:

Total sunlight, reduced to $25\%$ natural light and lowered to $5\%$ natural light conditions.

The weight of the dry plant is determined by different treatment conditions. The response component is also the plant's weight in the experiment.