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Producing Data: Experiments BPS chapter 9 © 2006 W.H. Freeman and Company Explanatory variables

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producing data experiments

Producing Data: Experiments

BPS chapter 9

© 2006 W.H. Freeman and Company

explanatory variables
Explanatory variables

Hirsch and Johnston from the Smell & Taste Treatment and Research Foundation in Chicago believe that the presence of floral scent can improve a person’s learning ability in some situations. To test this hypothesis, they set up an experiment in which each of 22 subjects completed 2 sets of three pencil and paper mazes, one set while wearing a floral-scented mask. Each subject wore a floral-scented mask and an unscented mask, and the order was randomized. The researchers measured the length of time it took each subject to complete the sets of mazes.

What is the explanatory variable?

  • 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.
explanatory variables answer
Explanatory variables (answer)

Hirsch and Johnston from the Smell & Taste Treatment and Research Foundation in Chicago believe that the presence of floral scent can improve a person’s learning ability in some situations. To test this hypothesis, they set up an experiment in which each of 22 subjects completed 2 sets of three pencil and paper mazes, one set while wearing a floral-scented mask. Each subject wore a floral-scented mask and an unscented mask, and the order was randomized. The researchers measured the length of time it took each subject to complete the sets of mazes.

What is the explanatory variable?

  • 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.
response variables
Response variables

Hirsch and Johnston from the Smell & Taste Treatment and Research Foundation in Chicago believe that the presence of floral scent can improve a person’s learning ability in some situations. To test this hypothesis, they set up an experiment in which each of 22 subjects completed 2 sets of three pencil and paper mazes, one set while wearing a floral-scented mask. Each subject wore a floral-scented mask and an unscented mask, and the order was randomized. The researchers measured the length of time it took each subject 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 pencil and paper mazes.
  • Whether the subject was able to complete the mazes quicker while wearing the floral-scented mask.
response variables answer
Response variables (answer)

Hirsch and Johnston from the Smell & Taste Treatment and Research Foundation in Chicago believe that the presence of floral scent can improve a person’s learning ability in some situations. To test this hypothesis, they set up an experiment in which each of 22 subjects completed 2 sets of three pencil and paper mazes, one set while wearing a floral-scented mask. Each subject wore a floral-scented mask and an unscented mask, and the order was randomized. The researchers measured the length of time it took each subject 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 pencil and paper mazes.
  • Whether the subject was able to complete the mazes quicker while wearing the floral-scented mask.
individuals
Individuals

Hirsch and Johnston from the Smell & Taste Treatment and Research Foundation in Chicago believe that the presence of floral scent can improve a person’s learning ability in some situations. To test this hypothesis, they set up an experiment in which each of 22 subjects completed 2 sets of three pencil and paper mazes, one set while wearing a floral-scented mask. Each subject wore a floral-scented mask and an unscented mask, and the order was randomized. The researchers measured the length of time it took each subject to complete the sets of mazes.

What are the individuals?

  • The masks (floral-scented or unscented).
  • The 22 subjects.
  • The mazes.
individuals answer
Individuals (answer)

Hirsch and Johnston from the Smell & Taste Treatment and Research Foundation in Chicago believe that the presence of floral scent can improve a person’s learning ability in some situations. To test this hypothesis, they set up an experiment in which each of 22 subjects completed 2 sets of three pencil and paper mazes, one set while wearing a floral-scented mask. Each subject wore a floral-scented mask and an unscented mask, and the order was randomized. The researchers measured the length of time it took each subject to complete the sets of mazes.

What are the individuals?

  • The masks (floral-scented or unscented).
  • The 22 subjects.
  • The mazes.
control
Control

Hirsch and Johnston from the Smell & Taste Treatment and Research Foundation in Chicago believe that the presence of floral scent can improve a person’s learning ability in some situations. To test this hypothesis, they set up an experiment in which each of 22 subjects completed 2 sets of three pencil and paper mazes, one set while wearing a floral-scented mask. Each subject wore a floral-scented mask and an unscented mask, and the order was randomized. The researchers measured the length of time it took each subject to complete the sets of mazes.

The researchers incorporated control/comparison by

  • Giving each subject a floral-scented and an unscented mask.
  • Randomly assigning half of the subjects to wear a floral-scented mask only and the other half to wear the unscented mask only.
  • Giving each subject two sets of mazes.
control answer
Control (answer)

Hirsch and Johnston from the Smell & Taste Treatment and Research Foundation in Chicago believe that the presence of floral scent can improve a person’s learning ability in some situations. To test this hypothesis, they set up an experiment in which each of 22 subjects completed 2 sets of three pencil and paper mazes, one set while wearing a floral-scented mask. Each subject wore a floral-scented mask and an unscented mask, and the order was randomized. The researchers measured the length of time it took each subject to complete the sets of mazes.

The researchers incorporated control/comparison by

  • Giving each subject a floral-scented and an unscented mask.
  • Randomly assigning half of the subjects to wear a floral-scented mask only and the other half to wear the unscented mask only.
  • Giving each subject two sets of mazes.
randomization
Randomization

Hirsch and Johnston from the Smell & Taste Treatment and Research Foundation in Chicago believe that the presence of floral scent can improve a person’s learning ability in some situations. To test this hypothesis, they set up an experiment in which each of 22 subjects completed 2 sets of three pencil and paper mazes, one set while wearing a floral-scented mask. Each subject wore a floral-scented mask and an unscented mask, and the order was randomized. The researchers measured the length of time it took each subject 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 that each subject receives the floral-scented and unscented masks.
randomization answer
Randomization (answer)

Hirsch and Johnston from the Smell & Taste Treatment and Research Foundation in Chicago believe that the presence of floral scent can improve a person’s learning ability in some situations. To test this hypothesis, they set up an experiment in which each of 22 subjects completed 2 sets of three pencil and paper mazes, one set while wearing a floral-scented mask. Each subject wore a floral-scented mask and an unscented mask, and the order was randomized. The researchers measured the length of time it took each subject 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 that each subject receives the floral-scented and unscented masks.
replication
Replication

Hirsch and Johnston from the Smell & Taste Treatment and Research Foundation in Chicago believe that the presence of floral scent can improve a person’s learning ability in some situations. To test this hypothesis, they set up an experiment in which each of 22 subjects completed 2 sets of three pencil and paper mazes, one set while wearing a floral-scented mask. Each subject wore a floral-scented mask and an unscented mask, and the order was randomized. The researchers measured the length of time it took each subject to complete the sets of mazes.

The researchers incorporated replication by

  • Using two masks.
  • Using two sets of mazes.
  • Using three mazes within each set.
  • Using twenty-two subjects.
  • Repeating the entire experiment a second time.
replication answer
Replication (answer)

Hirsch and Johnston from the Smell & Taste Treatment and Research Foundation in Chicago believe that the presence of floral scent can improve a person’s learning ability in some situations. To test this hypothesis, they set up an experiment in which each of 22 subjects completed 2 sets of three pencil and paper mazes, one set while wearing a floral-scented mask. Each subject wore a floral-scented mask and an unscented mask, and the order was randomized. The researchers measured the length of time it took each subject to complete the sets of mazes.

The researchers incorporated replication by

  • Using two masks.
  • Using two sets of mazes.
  • Using three mazes within each set.
  • Using twenty-two subjects.
  • Repeating the entire experiment a second time.
variables
Variables

Hirsch and Johnston from the Smell & Taste Treatment and Research Foundation in Chicago believe that the presence of floral scent can improve a person’s learning ability in some situations. To test this hypothesis, they set up an experiment in which each of 22 subjects completed 2 sets of three pencil and paper mazes, one set while wearing a floral-scented mask. Each subject wore a floral-scented mask and an unscented mask, and the order was randomized. The researchers measured the length of time it took each subject 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.
variables answer
Variables (answer)

Hirsch and Johnston from the Smell & Taste Treatment and Research Foundation in Chicago believe that the presence of floral scent can improve a person’s learning ability in some situations. To test this hypothesis, they set up an experiment in which each of 22 subjects completed 2 sets of three pencil and paper mazes, one set while wearing a floral-scented mask. Each subject wore a floral-scented mask and an unscented mask, and the order was randomized. The researchers measured the length of time it took each subject 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.
experimental design
Experimental design

Hirsch and Johnston from the Smell & Taste Treatment and Research Foundation in Chicago believe that the presence of floral scent can improve a person’s learning ability in some situations. To test this hypothesis, they set up an experiment in which each of 22 subjects completed 2 sets of three pencil and paper mazes, one set while wearing a floral-scented mask. Each subject wore a floral-scented mask and an unscented mask, and the order was randomized. The researchers measured the length of time it took each subject to complete the sets of mazes.

The experimental design used is called a

  • Completely randomized design.
  • Randomized block design.
  • Matched pairs design.
experimental design answer
Experimental design (answer)

Hirsch and Johnston from the Smell & Taste Treatment and Research Foundation in Chicago believe that the presence of floral scent can improve a person’s learning ability in some situations. To test this hypothesis, they set up an experiment in which each of 22 subjects completed 2 sets of three pencil and paper mazes, one set while wearing a floral-scented mask. Each subject wore a floral-scented mask and an unscented mask, and the order was randomized. The researchers measured the length of time it took each subject to complete the sets of mazes.

The experimental design used is called a

  • Completely randomized design.
  • Randomized block design.
  • Matched pairs design.
statistical significance
Statistical significance

If there is a statistically significant difference between the average times to complete the mazes while wearing the floral-scented mask and the unscented mask, then the difference in average times to complete the mazes between the floral-scented mask and the unscented mask is

  • Too large to be due to chance alone.
  • Too small to be due to chance alone.
  • So large that we can reasonably attribute it to chance.
  • So small that it is likely due to chance.
statistical significance answer
Statistical significance (answer)

If there is a statistically significant difference between the average times to complete the mazes while wearing the floral-scented mask and the unscented mask, then the difference in average times to complete the mazes between the floral-scented mask and the unscented mask is

  • Too large to be due to chance alone.
  • Too small to be due to chance alone.
  • So large that we can reasonably attribute it to chance.
  • So small that it is likely due to chance.
experimental design20
Experimental design

An Austrian study investigated whether maintaining a surgery patient’s body temperature close to normal by heating the patient during surgery decreases wound infection rates. Patients included in the study were undergoing colon or rectal surgery and were randomly assigned to one of two treatment groups. In the normalthermic group, patients’ core temperatures were maintained near normal 36.5 degrees Celsius. In the hypothermic group, patients’ core temperatures were allowed to decrease to about 34.5 degrees Celsius.

The design is called a

  • Completely randomized design
  • Randomized block design
  • Matched pairs design
experimental design answer21
Experimental design (answer)

An Austrian study investigated whether maintaining a surgery patient’s body temperature close to normal by heating the patient during surgery decreases wound infection rates. Patients included in the study were undergoing colon or rectal surgery and were randomly assigned to one of two treatment groups. In the normalthermic group, patients’ core temperatures were maintained near normal 36.5 degrees Celsius. In the hypothermic group, patients’ core temperatures were allowed to decrease to about 34.5 degrees Celsius.

The design is called a

  • Completely randomized design
  • Randomized block design
  • Matched pairs design
experimental design22
Experimental design

In the previous experiment involving patients’ temperatures, both men and women were the patients. If the men and women were separately assigned to treatments, the design would be a

  • Completely randomized design
  • Randomized block design
  • Matched pairs design
experimental design answer23
Experimental design (answer)

In the previous experiment involving patients’ temperatures, both men and women were the patients. If the men and women were separately assigned to treatments, the design would be a

  • Completely randomized design
  • Randomized block design
  • Matched pairs design
randomized block design
Randomized block design

In a randomized block design, a block contains

  • Individuals that are similar with respect to the characteristic that defines the block.
  • Individuals that are assigned to the same treatment.
  • Individuals that are similar with respect to the characteristic that defines the block and that are assigned to the same treatment.
randomized block design answer
Randomized block design (answer)

In a randomized block design, a block contains

  • Individuals that are similar with respect to the characteristic that defines the block.
  • Individuals that are assigned to the same treatment.
  • Individuals that are similar with respect to the characteristic that defines the block and that are assigned to the same treatment.
randomized block design26
Randomized block design

In a randomized block design

  • All of the subjects are allocated at random among the treatments.
  • The random assignment of individuals to treatments is carried out separately within each block.
  • All the individuals within one block are randomly assigned one treatment.
randomized block design answer27
Randomized block design (answer)

In a randomized block design

  • All of the subjects are allocated at random among the treatments.
  • The random assignment of individuals to treatments is carried out separately within each block.
  • All the individuals within one block are randomly assigned one treatment.
experimental design28
Experimental design

True or false: An advantage of the randomized block design (RBD) over the completely randomized design (CRD) is that the RBD eliminates confounding between a lurking variable (blocking variable) and the response variable.

  • True
  • False
experimental design answer29
Experimental design (answer)

True or false: An advantage of the randomized block design (RBD) over the completely randomized design (CRD) is that the RBD eliminates confounding between a lurking variable (blocking variable) and the response variable.

  • True
  • False
experimental design30
Experimental design

True or false: An advantage of the randomized block design (RBD) over the completely randomized design (CRD) is that the RBD eliminates the variation associated with the blocking variable and makes detection of statistical significance easier.

  • True
  • False
experimental design answer31
Experimental design (answer)

True or false: An advantage of the randomized block design (RBD) over the completely randomized design (CRD) is that the RBD eliminates the variation associated with the blocking variable and makes detection of statistical significance easier.

  • True
  • False
problems with experiments
Problems with experiments

A study claims that patients who receive surgery for intestinal cancer live much longer after treatment than patients who are treated without surgery. However, doctors operated only on patients in relatively good condition so we cannot conclude from this study that surgery lengthens intestinal cancer patients’ lives.

This is an example of

  • Confounding.
  • A lurking variable.
  • A double-blind experiment.
  • The placebo effect.
problems with experiments answer
Problems with experiments (answer)

A study claims that patients who receive surgery for intestinal cancer live much longer after treatment than patients who are treated without surgery. However, doctors operated only on patients in relatively good condition so we cannot conclude from this study that surgery lengthens intestinal cancer patients’ lives.

This is an example of

  • Confounding.
  • A lurking variable.
  • A double-blind experiment.
  • The placebo effect.
double blind experiments
Double-blind experiments

Medical experiments are often double-blind. This means that

  • All individual data are kept confidential.
  • Neither the subject nor the doctor/administrator knows which treatment the subject receives.
  • Doctors are not allowed to decide which treatment a patient will receive; subjects are randomly assigned to treatments.
  • The subjects in the control group receive a placebo treatment.
double blind experiments answer
Double-blind experiments (answer)

Medical experiments are often double-blind. This means that

  • All individual data are kept confidential.
  • Neither the subject nor the doctor/administrator knows which treatment the subject receives.
  • Doctors are not allowed to decide which treatment a patient will receive; subjects are randomly assigned to treatments.
  • The subjects in the control group receive a placebo treatment.
experiments
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.
experiments answer
Experiments (answer)

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.
experiments38
Experiments

Which of the following principles of good experimentation does an observational study not incorporate?

  • Control or comparison
  • Random assignment to treatments
  • Replication
experiments answer39
Experiments (answer)

Which of the following principles of good experimentation does an observational study not incorporate?

  • Control or comparison
  • Random assignment to treatments
  • Replication
experiment vs observational study
Experiment vs. observational study

The Minnesota Study of Twins Reared Apart investigated whether similar attributes of twins are related to heredity or the influence of family environment. The researchers conducted an intense psychological and physiological assessment of 56 pairs of identical twins reared apart and several hundred identical twins reared together and compared the similarities of the twins in both groups.

Is this study an experiment or an observational study?

  • Experiment
  • Observational study
experiment vs observational study answer
Experiment vs. observational study (answer)

The Minnesota Study of Twins Reared Apart investigated whether similar attributes of twins are related to heredity or the influence of family environment. The researchers conducted an intense psychological and physiological assessment of 56 pairs of identical twins reared apart and several hundred identical twins reared together and compared the similarities of the twins in both groups.

Is this study an experiment or an observational study?

  • Experiment
  • Observational study