In a study published in the journal Environmental Science and Technology in 2001, scientists were testing the endocrine disruptor hypothesis, which states that certain chemicals can interfere with hormone regulation in many organisms, leading to disorders such as the feminization of males. The scientists used juvenile fish and exposed them to either tap water or varying concentrations of treated sewage effluent (containing an array of chemicals). For this experiment, identify the control group, the treatment group, as well as the independent and dependent variables.

Control group - juvenile fish exposed to tap water

Independent variable - concentration of treated sewage effluent

Treatment group - juvenile fish exposed to sewage-treatment effluent

Dependent Variable -  juvenile male fish with female characteristics

Explanation:

In an experiment, a treatment group is the one which receives the treatment or the group on which experiment is being conducted. Thus, juvenile fishes that are exposed to other than normal condition (exposure to water) i.e sewage-treatment effluent is called the treatment group.  

A control group is the one which comprises of exposure of treatment group to normal condition so that the results can be compared with the group subjected to treatment. Here the normal condition is exposure to water. Hence, the juvenile fish exposed to tap water will be the control group  

An independent variable is the one which is varied during an experiment to study its impact on different treatment groups. Hence, concentration of treated sewage effluent

is the independent variable.

A dependent variable is the one which changes with the variation in the independent variable. Thus, percentage of male fish with female characteristics is the dependent variable