PH 310 Midterm 2 Test With
Complete Solution
Cohort study - ANSWER Groups are identified on basis of their exposure to risk factor or
treatment which is not under researchers control. The design can be either prospective
or retrospective. (Hazard ratio can be calculated)
Information bias - ANSWER A prejudice in the data that results when either the
respondent or the interviewer has an agenda and is not presenting impartial questions
or responding with truly honest responses, respectively.
Case-control study - ANSWER A type of epidemiological study where a group of
individuals with a disease (case), are compared to individuals without a disease
(controls). (Odds ratio can be calculated)
Selection bias - ANSWER A polling error in which the sample is not representative of the
population being studied, so that some opinions are over- or underrepresented. (Cohort
studies are subject to this kind of bias)
Cross-sectional study - ANSWER A study in which a representative cross section of the
population is tested or surveyed at one specific time. (Study design that is useful for
determining burden of disease on a population)
Questionnaires were mailed to every 10th person listed in the city telephone directory.
Each person was asked to list age, sex, smoking habits, and respiratory symptoms
during the preceding seven days. About 20% of the questionnaires were completed and
returned. About 10% of respondents reported having upper respiratory symptoms. What
type of study is this? - ANSWER Cross-sectional study
1,500 employees of a major air craft company were initially examined in 1951 and were
classified by diagnostic criteria for coronary artery disease (CAD). New cases of CAD
have been identified by examinations every three years and through death certificates.
Attack rates in different subgroups have been computed. What type of study is this? -
ANSWER Prospective cohort study
A random sample of middle-aged sedentary adults were selected from four census
tracts, and each person was examined for coronary artery disease (CAD). All persons
without disease were randomly assigned to either a two-year program of aerobic
exercise or a two-year arthritis-prevention non-aerobic exercise program. Both groups
were observed semi- annually for incidence of CAD. What type of study is this? -
ANSWER Randomized controlled trial/intervention trial
Randomized control trial - ANSWER A study in which people are allocated at random (by
, chance alone) to receive one of several clinical interventions.
A 39-year old woman presents with a mild sore throat, fever, malaise and headache and
is treated with penicillin, for presumed streptococcal infection. She returns in a week
with hypertension, fever, rash and abdominal pain. She responds favorably to
chloramphenicol, after a diagnosis of Rocky Mountain spotted fever is made. What type
of study is this? - ANSWER Case report. It is not usually regarded as an
"epidemiological" study, since there is no population, or comparison group.
Patients admitted for carcinoma of the stomach and patients without a diagnosis of
cancer are interviewed about their chewing tobacco history to assess the possible
association of chewing tobacco and gastric cancer. What type of study is this? -
ANSWER Case control study. This study includes both diseased and non-diseased
population for comparisons of previous exposure.
If one were conducting a study in sixth grade students to examine the association
between environmental tobacco smoke exposure and absence from school because of
respiratory illness, would it be important to adjust for confounding by age using either a
stratified analysis or regression analysis? - ANSWER False: There is no need to adjust
for age since it is associated with the exposure and outcomes but not in the immediate
causal pathway
Stratified analysis - ANSWER A statistical approach that allows you to test for
confounding and interaction.
Regression analysis - ANSWER Statistical method that allows you to examine the
relationship between two or more variables of interest
A researcher decides to investigate the risk factors for ALS. He gets a list of patients
from the neurologists' offices in his city and recruits neighbors of each patient to serve
as controls. What type of study design is this? - ANSWER Case control study
What type of study design can be either retrospective or prospective and is often used
when the investigators are interested in rare exposure? - ANSWER Cohort studies
True or false: Recall bias always results in an underestimate of the magnitude of
association. - ANSWER False
True or false: Prospective cohort studies are prone to selection bias as a result of
differences in the mechanism by which subjects initially are enrolled into the study. -
ANSWER True
True or false: Interviewer bias can produce either an overestimate or under-estimate of
the magnitude of association. - ANSWER True
True or false: Significant loss to follow up can cause an over-estimate or under-estimate
of the magnitude of association in a prospective cohort study. - ANSWER True
True or false: Case control studies are vulnerable to bias because both the exposure
Complete Solution
Cohort study - ANSWER Groups are identified on basis of their exposure to risk factor or
treatment which is not under researchers control. The design can be either prospective
or retrospective. (Hazard ratio can be calculated)
Information bias - ANSWER A prejudice in the data that results when either the
respondent or the interviewer has an agenda and is not presenting impartial questions
or responding with truly honest responses, respectively.
Case-control study - ANSWER A type of epidemiological study where a group of
individuals with a disease (case), are compared to individuals without a disease
(controls). (Odds ratio can be calculated)
Selection bias - ANSWER A polling error in which the sample is not representative of the
population being studied, so that some opinions are over- or underrepresented. (Cohort
studies are subject to this kind of bias)
Cross-sectional study - ANSWER A study in which a representative cross section of the
population is tested or surveyed at one specific time. (Study design that is useful for
determining burden of disease on a population)
Questionnaires were mailed to every 10th person listed in the city telephone directory.
Each person was asked to list age, sex, smoking habits, and respiratory symptoms
during the preceding seven days. About 20% of the questionnaires were completed and
returned. About 10% of respondents reported having upper respiratory symptoms. What
type of study is this? - ANSWER Cross-sectional study
1,500 employees of a major air craft company were initially examined in 1951 and were
classified by diagnostic criteria for coronary artery disease (CAD). New cases of CAD
have been identified by examinations every three years and through death certificates.
Attack rates in different subgroups have been computed. What type of study is this? -
ANSWER Prospective cohort study
A random sample of middle-aged sedentary adults were selected from four census
tracts, and each person was examined for coronary artery disease (CAD). All persons
without disease were randomly assigned to either a two-year program of aerobic
exercise or a two-year arthritis-prevention non-aerobic exercise program. Both groups
were observed semi- annually for incidence of CAD. What type of study is this? -
ANSWER Randomized controlled trial/intervention trial
Randomized control trial - ANSWER A study in which people are allocated at random (by
, chance alone) to receive one of several clinical interventions.
A 39-year old woman presents with a mild sore throat, fever, malaise and headache and
is treated with penicillin, for presumed streptococcal infection. She returns in a week
with hypertension, fever, rash and abdominal pain. She responds favorably to
chloramphenicol, after a diagnosis of Rocky Mountain spotted fever is made. What type
of study is this? - ANSWER Case report. It is not usually regarded as an
"epidemiological" study, since there is no population, or comparison group.
Patients admitted for carcinoma of the stomach and patients without a diagnosis of
cancer are interviewed about their chewing tobacco history to assess the possible
association of chewing tobacco and gastric cancer. What type of study is this? -
ANSWER Case control study. This study includes both diseased and non-diseased
population for comparisons of previous exposure.
If one were conducting a study in sixth grade students to examine the association
between environmental tobacco smoke exposure and absence from school because of
respiratory illness, would it be important to adjust for confounding by age using either a
stratified analysis or regression analysis? - ANSWER False: There is no need to adjust
for age since it is associated with the exposure and outcomes but not in the immediate
causal pathway
Stratified analysis - ANSWER A statistical approach that allows you to test for
confounding and interaction.
Regression analysis - ANSWER Statistical method that allows you to examine the
relationship between two or more variables of interest
A researcher decides to investigate the risk factors for ALS. He gets a list of patients
from the neurologists' offices in his city and recruits neighbors of each patient to serve
as controls. What type of study design is this? - ANSWER Case control study
What type of study design can be either retrospective or prospective and is often used
when the investigators are interested in rare exposure? - ANSWER Cohort studies
True or false: Recall bias always results in an underestimate of the magnitude of
association. - ANSWER False
True or false: Prospective cohort studies are prone to selection bias as a result of
differences in the mechanism by which subjects initially are enrolled into the study. -
ANSWER True
True or false: Interviewer bias can produce either an overestimate or under-estimate of
the magnitude of association. - ANSWER True
True or false: Significant loss to follow up can cause an over-estimate or under-estimate
of the magnitude of association in a prospective cohort study. - ANSWER True
True or false: Case control studies are vulnerable to bias because both the exposure
