Attached is the complete problem that I found on the internet.
First question.
The constants (variables that stay the same throughout the study for all groups) were the hours of light per day, the amount and frequency of food that was given, the surrounding settings such as the presence of a wheel for exercise and the cage size, T0 (time at which all the rats were measured for the experiment purposes), and days under the experiment.
Second question.
The independent variable (variable that we control in order to study the dependent variable) is the time.
Third question.
The dependent variable (variable that we pretend to analyse under the set conditions) can be either the rats' weight or length.
Fourth question.
During the experiment I need to collect data related to the conditions of the experiment, whether they are being constant or not. Data such as temperature, hours of light, food given, etc.
Fifth question.
There is a flaw on the formation of the groups. The groups should be balanced in all the demographic characteristics, such as length and weight, and also balanced in number of rats. The total number of rats is nine, so the most acceptable would be to have 3 rats per group of study and not 4 or 2, an in the last two groups. As for the demographic characteristics, it should be taken into consideration the initial length and weight of each rat before grouping them so that the groups in themselves were not a variable. As we can observe there is a great variation, mostly on the last group, made up only of two rats, one of average weight and length and the other with the lowest length and weight.
Sixth question.
At a medium temperature (70ºF) there seems to be a greater increase of weight, between 40 to 55 grams more. In the other groups there's an increase of weight as well but more discreet. The group exposed at a higher temperature (85ºF) had a weight gaining of 23 to 32 grams, and the group exposed to a lower temperature (50ºF) gained from 9 to 20 grams. Temperature might be related to the weight gaining but not in a directly proportional way.
Considering now the length, there seems to be no significant changes related to the temperatures of 70ºF and 85ºF. In these cases the rats increased in length in a like manner way. What was evident though, was that the rats on the group exposed to the lowest temperature (50ºF) had only grown from 0 to 0.2 cm even with some weight gaining that clearly was not accompanied by the length. Temperature might be related to the length of the rats: lower temperatures inhibit rats' growth.
