hii. iwould need help in this question with some explanation for my assignment w

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hii.
iwould need help in this question with some explanation for my assignment within 5 hours .
thank you

3. (9 marks) I don't like eating over-ripe bananas, and am interested in understanding the factors that influence the ripening time of bananas after I bring them home from the store (which I define as the time until a brown spot appears). I decide to conduct an experiment. Every Sunday for 8 weeks, I buy a bunch of 6 green/yellow bananas, and record the time until the first brown spot appears on each banana (so that I end up with 48 measurements on ripening time). Each week, I try a different combination of methods of storing the bananas ("treatment): in a dark cupboard or in the light, with or without an ethylene absorber, and close to or far away from other produce (fruits and vegetables). The details of my storage plans are as follows: Week Dark/Light Ethylene Absorber? Close to Other Produce? 2 Dark Dark Dark 5 Light 6 Light 7 Light 8 Light Dark es 3 No Yes No Yes No Yes No Yes Yes No a. What are the factors in this experiment, and what are the corresponding levels? (2 marks) b. What are the individuals in this experiment? (1 mark) c. Did I use a completely randomized design? Explain. (2 marks) d. I find that the bananas that I stored in the dark with an ethylene absorber away from other produce had a longer ripening time than the bananas in other bunches. Would you suspect that this storage method causes longer ripening time, or that a confounding factor was at play? Explain and, if the latter, provide a plausible example of such a factor. (2 marks) Suggest an improvement to my experimental design (other than increasing my sample size). (2 marks) e.

Explanation / Answer

a) A factor of an experiment is a controlled independent variable; a variable whose levels are set by the experimenter.

The factors in this experiment are the factors which are changed and controlled to measure the ripening time.

The factors and their levels are :

i) Lighting - Dark/Light

ii) Ethylene absorber - Yes/No

iii) Closeness to other produce - Yes/No

b) This is the response variable which is the ripening time for the bananas. (Time from purchase till a brown spot appears)

c) The design is a form of cyclic randomization. Think of the 3 bit pattern going from 000 to 001 to 010 till 110 to 111. In the 8 weeks, all 8 possible different configurations are achieved. (dark/light x ethylene yes/no x closeness yes/no) So yes, this is a form of a completely randomized experiment where the factors of the experiment are left to be under randomness.

d) The point to note in this question is that 'causes' has been underlined. When we say x causes y, that means whenever x occurs, y HAS to occur. Such a link of causation cannot be proved here. It is after all just one instance of an experiment. Perhaps if someone else were to perform the experiment under the same conditions, he would have gotten a different result. For example, a confounding factor that would have been here can be the state of the bananas itself. Maybe that day, the bananas purchased were extremely fresh and straight from the farm, and this is why these bananas had a longer ripening time.  

e) An improvement that could be made would perhaps be to introduce a second stage to the experiment. Even after completing the 8 week experiment, there is a degree of inconclusiveness or uncertainty regarding the final result. Can we be completely sure that condition C increases ripening time or is condition F the worst for the bananas? We can observe the top 3 or 4 conditions where the ripening time was maximum. Repeat the experiment with only those 3 or 4 conditions which would hence take 3 or 4 weeks and then check the ripening time for each. Depending on the 2nd experiment result along with the 1st experiment, then we can calculate and be sure of the overall result and make a final certain conclusion with a degree of confidence.

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