Question

2. Researchers were interested in evaluating the effects of two low-fat diets with and without resistance exercise training (RT) on weight loss. The diets differed in the carbohydrate-to-protein ratio. A total 80 individuals with type 2 diabetes participated in the study. There were 40 men and 40 women and each group was randomly assigned to an isocaloric diet of either standard or high protein, with or without supervised resistance training (3 days/week) for 16 weeks. Body weight was measured before and after the study. (a) Identify the experimental unit in this study. [1 mark (b) What is/are the factor(s) for this experiment? [1 mark] (c) List all the treatments in this experiment. 2 marks (d) Identify the response variable. [1 mark (e) Identify whether or not the study involves any of the following. i. blindinjg ii. blocking Briefly explain your answer. [2 marks (f) Draw a suitable diagram showing how you would design this experiment. (See lecture notes or textbook for such diagrams). [3 marks] (g) Describe an advantage of random assignment of treatment. [1 mark

Answer 1

(a) Experimental unit

It is the entity to which a specific treatment combination is applied. Individual Man/ Woman is the Experimental Unit.

(b) Factor(s) for this experiment

An independent variable whose levels are set by the experimenter is factor. Here, factors are Training, Diet, Gender with 2 levels each. See the TABLE below:

TABLE	Supervised Resistance Training (Treatment)			Low-fat diets (Treatment)			Gender			Body Weight recorded
Level 1	RT1	with RT		D1	Standard protein diet		M	Man		B	Before study
Level 2	RT2	without RT		D2	High protein diet		W	Woman		A	After study

(c) All the treatments in this experiment

An object whose effect is to be measured and compared is called as a treatment. Here, Training (RT1 &RT2), Diet(D1 & D2) are treatments with two levels each.

(d) The Response variable

The dependent variable affected during experiment is called response variable. The body weight of the individual is the response variable.

(e) Identify whether or not the study involves i. Blinding ii. Blocking.

Blinding in the experiment means one or more individuals are kept unaware about the treatment assigned to him/her; specifically to avoid the possible BIAS in the study. Here, blinding training doesn't seem appropriate. (However, blinding can be done while diet application; to avoid bias : human bias by staff or anyone; weak person administered high protein diet.)

Blocking is the non-random arrangement of experimental units into groups (called blocks) consisting of units that are similar to one another. Here, blocking is suitable like Training (RT1 & RT2), Gender(Men and Women)..

(f) Suitable diagram showing how to design this experiment

It seems 2³ factorial experiment (8 combination of treatments in all). We don't know the number of men assigned to treatment: RT1-D1.

Before conducting experiment, we already have the "body weights (before study)" of individuals.

Diagram: Notations as described in the table above.

Diet	D1	D2
Training
RT1	M	M
	W	W
RT2	M	M
	W	W

(g) Advantage of random assignment of treatment

To minimize error. To avoid bias between men and women (men generally considered to be physically healthy and inclined to training than women).