Question

What’s the design? Read the brief report of statistical research below, and
a) explain why it is an experiment rather than an observational study.

Is obesity related to stress?
Some mice were subjected to stress and then fed either a standard diet or a high-fat diet.
A group of non-stressed mice were also fed a standard or high-fat diet.
The weights were recorded for all the mice, before and after the study.

Also, identify:
b) the factor(s) in the experiment and the number of levels for each.
c) the number of treatments.
d) the response variable(s) measured.
e) whether it was blind (or double-blind)
f)the nature and scope of the conclusion the experiment can reach.

Answer 1

a.

Here stressed mice are randomly assigned to one of two groups and one group receives the standard diet while the other group receives high-fat diet. Similarly non-stressed mice are randomly assigned to one of two groups and one group receives the standard diet while the other group receives high-fat diet. Therefore here researcher introduces an intervention and study the effects of diet and stress on obesity. Hence it is experimental study rather observational.

b. Here two factors are used and the factors are: stress and diet and each factor has two levels. Levels of stress: stressed and non-stressed and levels of diet: standard diet and high-fat diet.

c. No. of treatment combinations=4 ((stressed, standard diet), (stressed, high-fat diet),  (non-stressed, standard diet), (non-stressed, high-fat diet))

d. Response variable=gain in weight of the mice i.e. weight of mice after study-weight of mice before the study

e. It was a double-blind.

f. From this study we get an idea about the main effect of diet, stress and their interaction.