Question

2) 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 in the below table:

(Week) (Dark/Light) (Ethylene Absorber?) (Close to Other Produce?)
1 Dark Yes Yes
2 Dark Yes No
3 Dark No Yes
4 Dark No No
5 Light Yes Yes
6 Light Yes No
7 Light No Yes
8 Light No No

a. What are the factors in this experiment, and what are the corresponding levels?

b. What are the individuals in this experiment?

c. Is this a randomized controlled experiment? Explain.

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.

e. Suggest an improvement to my experimental design (other than increasing my sample
size).

Answer 1

a. The factors and their levels in the experiment are -

1. Light - Levels - Dark, Light

2. Ethylene Absorber - Levels - Yes, No

3. Close to Other Produce -  Levels - Yes, No

b.

The  individuals in this experiment are green/yellow bananas.

c.

As, each week, random green/yellow bananas are given all combinations of treatments - (Dark/Light) (Ethylene Absorber - Yes/No) (Close to Other Produce - Yes/No), this is a randomized controlled experiment.

d.

There are confounding factors at play which had led to a longer ripening time when the bananas were stored in the dark with an ethylene absorber away from other produce. The possible confounding variables are

1. It is known that bananas ripe faster in high tempeartures. Storing in dark, may have reduced the temperature which consequently have reduced the ripening rate of bananas. Hence low temperature is a confounding factor.

2. Presence of Ethyelene acceleartes ripening. During ripening, Bananas produces excess amount of ethylene. If they are stored in Ethylene Absorber, excess ethylene is absorbed which may have reduced the ripening rate of bananas. Hence absence of ethylene is another confounding factor.

3. If the bananas are away from other produce, there is less chance of fungi, bacteria and ethylene from the other produce affect bananas. Fungi, bacteria and ethylene increases the ripening rate of bananas. So, bananas away from other produce may have longer ripening time due to fungi, bacteria affect from other produce. Hence, absence of fungi, bacteria and ethylene are another confounding factors.