Question

1) In each scenario below, specify each variable as a response variable, an explanatory variable, or neither.

a. A researcher collects measurements of VO2 max and resting heart rate on a group of
subjects to study the relationship between these two variables.

b. A real estate agent wants to be able to predict selling prices of houses in Vancouver. He
collects data on 100 recently sold houses, recording their selling prices, size, age, number
of bedrooms, and whether they had a suite.

c. A physicist is investigating particle decay rates. She conducts a series of experiments,
recording in each the number of remaining particles at each time point.

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

In each scenario below, specify each variable as a response variable, an explanatory variable, or neither.

Definition: (First let's understand the two types of the variable)

The value of the explanatory variable is thought to partially explain the value of the response variable for an individual. The identification of one variable as “explanatory” and the other as “response” does not imply that there is a causal relationship. It simply implies that knowledge of the value of the explanatory variable may help provide knowledge about the value of the response variable for an individual.

a. A researcher collects measurements of VO2 max and resting heart rate on a group of subjects to study the relationship between these two variables.

VO2 max & Heart Rate: Both are response variable.

As the question does not specify the study so we cannot make out what is being explained.

b. A real estate agent wants to be able to predict selling prices of houses in Vancouver. He collects data on 100 recently sold houses, recording their selling prices, size, age, number of bedrooms, and whether they had a suite.

Selling prices; Response variable

Size, Aage, Number of bedrooms and whether they had a suite: explanatory variable

Because Size, Aage, Number of bedrooms and whether they had a suite (explanatory variable) of the house may affect the selling the price(response variable) of the house.

c. A physicist is investigating particle decay rates. She conducts a series of experiments, recording in each the number of remaining particles at each time point.

Time: explanatory variable

Number of remaining particle: Response variable

The decay rate of the particle which is measured in terms of the number of particles (response variable) can be explained with the time (explanatory) lapsed.

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

Factors:

1. in a dark cupboard or in the light, Levels: 2 (Dark/Light)

2. with or without an ethylene absorber, Levels: 2 yes/No

3. close to or far away from other produce (fruits and vegetables) Levels: 2 Yes/No

b) What are the individuals in this experiment?

6 Bananas

c. Is this a randomized controlled experiment? Explain.

A randomized experiment is a study in which treatments are randomly assigned to participants and the one which reduces the bias.

However, you could have selection bias and response bias. Because your choice of banana is not random. Moreover teh response could be biased by the temperature or the color of banana. if you strated with yellow it will ripe faster and if ypou started with green it will ripe later.

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.

Amount of humidity could be a confounding factor.

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

You can include temperature which could be a strong factor. Also, you can include the color of banana (yellow, green)