Researchers asked a sample of 50 1st grade teachers and a sample of 50 12th grade teachers how much of their own money they spent on school supplies in the previous school year. They wanted to see if...

Lesson Assignment #10
1

Answer the following questions and submit for grading. Each question or part of a
question is worth 1 point.

1. Researchers asked a sample of 50 1st grade teachers and a sample of 50 12th grade
teachers how much of their own money they spent on school supplies in the
previous school year. They wanted to see if teachers at one grade level spend more
than teachers at the other grade level.

a. What type of study is found—observational or randomized experiment?
Explain.
This is an observational experiment because here we are comparing two
treatments –50 1st grade teachers and a sample of 50 12th grade teachers. It
observes differences in the explanatory variable and notice whether these are
related to differences in the response variable.

b. What is the experimental (or observational) unit?
The experimental unit is the money each of them spent on school supplies

c. What is the response variable?
Money that teachers spent on the school supplies is the response variable.

d. What is the explanatory variable?
Explanatory variable is the grade level

e. Do we have to worry about confounding variables in this instance? Why? If so
identify a possible confounding variable?
Yes, we do have to worry about the confounding variables in this instance as
they affect the response variable and are related to the explanatory variable.
Confounding variables are Salary of teachers, experience

f. Are either of the terms retrospective study or prospective study relevant?
Explain.
In this case, retrospective study is relevant as teachers are asked to recall their
money spent on school supplies in previous school year

2. A research team compared two methods of measuring tread wear on tires. Eleven
tires were each measured for tread wear by two different methods: one method was
based on weight while the other method was based on groove wear. For
convenience, each tire was measured first by weight method and then second by
the groove wear.

a. The two samples are which of the following: two independent or two dependent
(matched pairs)? Explain.
The two samples are matched pairs because the members of one sample can be
used to determine the members of the other sample.

b. What type of study is found—observational or randomized experiment?
Explain.
This type of study is an example of randomized experiment. This is because if
we randomize all the tires and drew a sample, the experiment would not be
same as the intended experiment. Therefore, they are matched pairs.

c. What is the experimental (or observational) unit?
Observational unit is measuring tread wear on tires

d. What is the response variable?
Tread wear on tires is the respective response variable

d. What is the explanatory variable?
Methods measuring weight


3. A study wants to determine if taking fish oils can reduce depressive symptoms. A
group of 50 volunteers who suffered from mild depression were randomly divided
into two groups. Each person was given a three-month‘s supply of capsules. One
group was given capsules that contained fish oils while the other group was given
capsules that look and tasted like fish oils, but actually only contained sugar.
Neither the participants nor the investigator knew what type of capsule they were
taking. At the end of the month, a psychologist evaluated them to determine if their
depressive symptoms had changed. Therefore, we are comparing the "change in
depressive symptoms" for these individuals in the two groups. Explain whether
each of the following terms applies to this study.

a. observational study

b. randomized experiment

c. placebo

d. placebo effect

e. single-blind

f. double-blind

g. matched pairs (dependent samples)

h. block design

i. independent samples

j. explanatory variable (What is it?) - Effect of capsule with fish oil and with
sugar

k. response variable (What is it?) – Change in depressive symptoms

Some of the key terms are related to this experiment. They are:
1. Observational experiment: It observes differences in the capsule with fish oil or
with sugar and notice whether these are related to differences in the response
variable i.e. reduction in depression symptoms
2. Matched pairs: This is because the members of one sample can be used to
determine the members of the other sample and hence helps in evolving the
impact on response variable.
3. Block design: This is because here experimental units are grouped into
homogeneous blocks within which each treatment occurs c times (usually c=1).

4. Does the use of cell phones lead to a higher incidence of brain cancer? People with
brain cancer were matched with people who did not have brain cancer on age,
gender, and living environment. Each participant in the study was asked to answer
questions about previous life experiences and exposures. Determine whether or
not each of the following terms applies to this observational study.

a. prospective

b. retrospective

c. case-control study

In this study, all these words are applicable because use of cell phones leading to a
higher incidence of brain cancer is dependent on the existing and previous information
and is likely to have the similar observation in future. It is also a case-control study
because here two existing groups differing in outcome are identified and compared on
the age, gender and living environment. This is basically to compare the participants
who have brain cancer with those who do not have.

5. A study involving ten people wants to compare the effectiveness of two different
brands of antihistamines with regard to enhancing sleep. Each person is randomly
assigned to take either Antihistamine A or Antihistamine B on the first night. Then
each takes the other antihistamine on the following night. With each person, the
hours of sleep were recorded for each night. Explain whether each of the following
terms applies to this study.

a. observational study

b. randomized experiment

c. carry-over effect (confounding)

d. matched pairs (dependent samples)

e. explanatory variable (What is it?)

f. response variable (What is it?)

This is because this study creates differences in the effectiveness of two different
brands of antihistamines and examines the hours of sleep for those ten individuals and...