Question

Consider the following studies:
Study 1: A study was conducted to investigate the effects of alcohol consumption on handeye
co-ordination. 200 people were interviewed and their level of alcohol consumption
over the previous five years was assessed and classified as either low, medium or high.
Each person was then given a series of tasks resulting in a hand-eye co-ordination score.

Study 2: A study was conducted to investigate the efficacy of a new iron tablet compared to a
currently used iron tablet. It is known that the level of efficacy for iron tablets is different
for males and females. 200 people were available for the study. First, they were divided
into males and females. Then these two groups were randomly split in half – one half was
given the new tablet, while the other half was given the existing tablet. At the start of the
study, all participants were given blood tests and their iron levels measured. After six
weeks of taking the iron tablets, they were given another blood test and their iron levels
measured again. For each subject, the difference in iron levels was recorded. The average
of the differences were then compared separately for males and females.

(a) Answer the following questions FOR EACH study:
(i) Identify the groups that are being compared. (I.e., what treatments or factors of interest
are being compared?) DO NOT also say what is being measured to make the
comparison – you do this in (ii).
(ii) What is being measured to compare these groups? ONLY describe the variable being
measured. DO NOT also mention the groups being compared – you do this in (i).
(iii) Would you describe the study as an experiment or an observational study?
- If it was an experiment, what part of the study design led you to this conclusion?
- If it was an observational study, could an experiment have been easily carried out
instead? If so, briefly explain how. If not, briefly explain why not

Answer 1

Consider the following studies:
Study 1: A study was conducted to investigate the effects of alcohol consumption on handeye
co-ordination. 200 people were interviewed and their level of alcohol consumption
over the previous five years was assessed and classified as either low, medium or high.
Each person was then given a series of tasks resulting in a hand-eye co-ordination score.

(a) Answer the following questions FOR EACH study:
(i) Identify the groups that are being compared. (I.e., what treatments or factors of interest
are being compared?) DO NOT also say what is being measured to make the
comparison – you do this in (ii).

The groups that are compared are people and their hand-eye co-ordination score.

(ii) What is being measured to compare these groups? ONLY describe the variable being
measured. DO NOT also mention the groups being compared – you do this in (i).

To compare these groups, their alcohol consumption over the previous five years was assessed.

(iii) Would you describe the study as an experiment or an observational study?

This study is an observational study because 200 people were interviewed and their level of alcohol consumption over the previous five years was assessed and classified as either low, medium or high.
Study 2: A study was conducted to investigate the efficacy of a new iron tablet compared to a
currently used iron tablet. It is known that the level of efficacy for iron tablets is different
for males and females. 200 people were available for the study. First, they were divided
into males and females. Then these two groups were randomly split in half – one half was
given the new tablet, while the other half was given the existing tablet. At the start of the
study, all participants were given blood tests and their iron levels measured. After six
weeks of taking the iron tablets, they were given another blood test and their iron levels
measured again. For each subject, the difference in iron levels was recorded. The average
of the differences were then compared separately for males and females.

(a) Answer the following questions FOR EACH study:
(i) Identify the groups that are being compared. (I.e., what treatments or factors of interest
are being compared?) DO NOT also say what is being measured to make the
comparison – you do this in (ii).

The groups that are compared are people and the efficacy for iron tablets.

(ii) What is being measured to compare these groups? ONLY describe the variable being
measured. DO NOT also mention the groups being compared – you do this in (i).

To compare these groups, the difference in iron levels was recorded.

(iii) Would you describe the study as an experiment or an observational study?

This study is an experimental study because two groups were randomly split in half – one half was
given the new tablet, while the other half was given the existing tablet. At the start of the
study, all participants were given blood tests and their iron levels measured.