Transcript Clicker_chapter9.ppt

Producing Data: Experiments
BPS chapter 9
© 2006 W.H. Freeman and Company
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?
a)
b)
c)
d)
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)
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?
a)
b)
c)
d)
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
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?
a)
b)
c)
d)
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)
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?
a)
b)
c)
d)
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
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?
a)
b)
c)
The masks (floral-scented or unscented).
The 22 subjects.
The mazes.
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?
a)
b)
c)
The masks (floral-scented or unscented).
The 22 subjects.
The mazes.
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
a)
b)
c)
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)
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
a)
b)
c)
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
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
a)
b)
c)
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 floralscented and unscented masks.
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
a)
b)
c)
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
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
a)
b)
c)
d)
e)
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)
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
a)
b)
c)
d)
e)
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
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
a)
b)
c)
d)
An explanatory variable.
A response variable.
A lurking variable.
Confounded with floral scent.
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
a)
b)
c)
d)
An explanatory variable.
A response variable.
A lurking variable.
Confounded with floral scent.
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
a)
b)
c)
Completely randomized design.
Randomized block design.
Matched pairs design.
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
a)
b)
c)
Completely randomized design.
Randomized block design.
Matched pairs design.
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
a)
b)
c)
d)
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)
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
a)
b)
c)
d)
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 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
a)
b)
c)
Completely randomized design
Randomized block design
Matched pairs design
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
a)
b)
c)
Completely randomized design
Randomized block design
Matched pairs design
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
a)
b)
c)
Completely randomized design
Randomized block design
Matched pairs design
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
a)
b)
c)
Completely randomized design
Randomized block design
Matched pairs design
Randomized block design
In a randomized block design, a block contains
a)
b)
c)
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)
In a randomized block design, a block contains
a)
b)
c)
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
In a randomized block design
a)
b)
c)
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 (answer)
In a randomized block design
a)
b)
c)
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 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.
a)
b)
True
False
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.
a)
b)
True
False
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.
a)
b)
True
False
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.
a)
b)
True
False
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
a)
b)
c)
d)
Confounding.
A lurking variable.
A double-blind experiment.
The placebo effect.
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
a)
b)
c)
d)
Confounding.
A lurking variable.
A double-blind experiment.
The placebo effect.
Double-blind experiments
Medical experiments are often double-blind. This means that
a)
b)
c)
d)
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)
Medical experiments are often double-blind. This means that
a)
b)
c)
d)
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
An advantage of experiments over observational studies is
a)
b)
c)
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)
An advantage of experiments over observational studies is
a)
b)
c)
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
Which of the following principles of good experimentation does an
observational study not incorporate?
a)
b)
c)
Control or comparison
Random assignment to treatments
Replication
Experiments (answer)
Which of the following principles of good experimentation does an
observational study not incorporate?
a)
b)
c)
Control or comparison
Random assignment to treatments
Replication
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?
a)
b)
Experiment
Observational study
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?
a)
b)
Experiment
Observational study