A group of scientists is conducting an experiment on the effects of media on children. They randomly select 100 children and randomly assign each child to one of four treatment groups. Each treatment group has a specific amount of screen time during a one-week time frame. The first group has no screen time, the second group has two hours of screen time, the third group has four hours of screen time, and the fourth group has six hours of screen time. After the first week, the scientists conduct the same experiment, with the same subject groups, for three more weeks so that each group experiences each of the four treatments. Which statements about this study are true? This study uses blocking. This study uses a control group. This study uses a repeated measures design. This study uses blinding. This study uses random sampling.

Blocking is a technique used in experimental design to account for potential sources of variation. In this case, there is no explicit mention of blocking. Blocking typically involves grouping subjects based on certain characteristics before random assignment to treatments, which isn't described here.

False.

This study uses a control group.

A control group is a group that does not receive the experimental treatment and is used as a baseline to compare the effects of the treatment. The first group with no screen time can be considered a control group.

True.

This study uses a repeated measures design.

In a repeated measures design, the same subjects are exposed to all treatments. Since each child in the study experiences all four levels of screen time over four weeks, this is indeed a repeated measures design.

True.

This study uses blinding.

Blinding involves keeping the subjects, experimenters, or both unaware of which treatment the subjects are receiving to prevent bias. There is no information in the description indicating that blinding was used.

False.

This study uses random sampling.

Random sampling refers to the method of selecting subjects from a population in a way that each subject has an equal chance of being chosen. The description states that 100 children were randomly selected, indicating the use of random sampling.

True.