10Level of Threonineiv) What nuisance factor(s) that was/were held constant? Age and gender of the ratsB) How many observations in this experiment? Since the error is a function of subjects (rats): Error(factor(Subject)). What is the degree of freedom for the residuals? Sample size = 180 matured male ratesObservations = number of groups * treatments = 5*9 = 45Degree of freedom for the residuals = 45-9 = 36C) What kind of experimental design used in this experiment? List the between block verses within block nuisance factors for this experiment. The experimental design used in this experiment is randomized complete block design (RCBD), as evidenced by the grouping of experimental units into blocks and random assignment of units to the treatments