Producing Data: Experiments

An advantage of experiments over observational studies is

• An experiment can provide evidence of cause and effect.
• An experiment can compare two or more groups.
• An experiment can include explanatory and response variables.

The Minnesota Study of Twins Reared Apart investigated whether attributes of twins are related to heredity or environment. The researchers assessed 56 pairs of identical twins reared apart as well as several hundred identical twins reared apart.  They compared the similarities of the twins in both groups.
Is this an experiment or an observational study?

• Experiment
• Observational study

In a famous study, 5200 patients were categorized into 2 groups according to their soda habit.  After 4-years of follow-up, the rate of heart disease was higher in the regularly drank group than the sparingly drank group.  Does soda cause heart disease?

• Yes because this is an experiment.
• No because this is an observational study.
• Can't say because this is an observational study.

Researchers believed that floral scent can sometimes improve a person's learning ability.  They set up an experiment in which each of 22 subjects completed sets of mazes.  Each subject wore a floral-scented mask and an unscented mask in random order.  The researchers measured the time to complete the sets of mazes.
What is the explanatory variable (factor)?

• The amount of scent.
• Presence or absence of the floral scent.
• Time to complete the pencil and paper mazes.
• Whether the subject was able to complete the mazes quicker while wearing the floral scented mask.

Researchers believed that floral scent can sometimes improve a person's learning ability.  They set up an experiment in which each of 22 subjects completed sets of mazes.  Each subject wore a floral-scented mask and an unscented mask in random order.  The researchers measured the time to complete the sets of mazes.
What is the response variable?

• The amount of scent.
• Presence or absence of the floral scent.
• Time to complete the mazes.
• Whether the subject  was able to complete the mazes quicker while wearing the floral scented mask.

Researchers believed that floral scent can sometimes improve a person's learning ability.  They set up an experiment in which each of 22 subjects completed sets of mazes.  Each subject wore a floral-scented mask and an unscented mask in random order.  The researchers measured the time to complete the sets of mazes.
What are the individuals?

• The mask.
• The 22 subjects.
• The mazes

Researchers believed that floral scent can sometimes improve a person's learning ability.  They set up an experiment in which each of 22 subjects completed sets of mazes.  Each subject wore a floral-scented mask and an unscented mask in random order.  The researchers measured the time to complete the sets of mazes.
If age affects whether the presence of a floral scent improves learning ability and was not included among the variables studied in the experiment, then age is

• an explanatory variable
• a response variable
• a lurking variable
• confounded with floral scent

Researchers believed that floral scent can sometimes improve a person's learning ability.  They set up an experiment in which each of 22 subjects completed sets of mazes.  Each subject wore a floral-scented mask and an unscented mask in random order.  The researchers measured the time to complete the sets of mazes.
The researchers incorporated randomization by

• Randomly selecting the subjects to participate in the study.
• Randomly assigning half of the subjects to wear the floral-scented mask and the other half to wear an unscented mask.
• Randomly assigning the order each subject receives the floral-scented and unscented masks.

Researchers believed that floral scent can sometimes improve a person's learning ability.  They set up an experiment in which each of 22 subjects completed sets of mazes.  Each subject wore a floral-scented mask and an unscented mask in random order.  The researchers measured the time to complete the sets of mazes.
The experimental design is a

• completely randomized design
• matched pair design
• randomized block design

An Austrian study investigated whether maintaining a surgery patient's body temperature close to normal during surgery decreases infection rates.  Patients in the study were randomly assigned to one of two treatment groups, a normal-thermic group and a hypothermic group.
Both men and women were included in the study although it was believed that men would react differently to the treatments than women.  If the randomization to treatments was carried separately for men and women, the design would be a

• completely randomized design
• randomized block design
• matched pairs design