As men age. their testosterone levels gradually decrease. This may cause a reduction in energy. an increase in fat. and other undesirable changes. Do testosterone supplements reverse some of these effects? A study in the Netherlands assigned 23'? men aged 60 to 30 with low or lownormal testosterone levels to either a testosterone supplement or a placebo. Why is it necessary to include a control group in this experiment? 0 Every experiment needs a control group in order to make proper comparisons between treatments. 0 A control group is necessary to balance the effects of other variables among the treatment groups. 0 A control group is necessary so any differences in the effects of the treatments can be distinguished from chance differences between the groups. 0 A control group helps avoid confounding and reduces variability in the response variable. O A control group is used to provide a baseline for comparing the effects of other treatments