Transcript Stats Review

Stats Review
Identify the appropriate statistic
• A researcher randomly assigns five
individuals to receive a new experimental
procedure and five to a control condition.
At the end of the study, all 10 are
measured. Scores for those in the
experimental group were 7, 6, 9, 7, and 6.
Scores for those in the control group were
5, 2, 4, 3, and 6.
Identify the appropriate statistic
• A researcher randomly assigns five
individuals to receive a new experimental
procedure and five to a control condition.
At the end of the study, all 10 are
measured. Scores for those in the
experimental group were 7, 6, 9, 7, and 6.
Scores for those in the control group were
5, 2, 4, 3, and 6.
– Independent measures t-test
Identify the appropriate statistic
• An experiment compares the effects of
four treatments, giving each treatment to
20 participants and then assessing their
performance on a standard measure.
Identify the appropriate statistic
• An experiment compares the effects of
four treatments, giving each treatment to
20 participants and then assessing their
performance on a standard measure.
– One way ANOVA
Identify the appropriate statistic
• A medical researcher has heard anecdotal evidence that certain
anti-depressive drugs can have the positive side-effect of
lowering neurological pain in those individuals with chronic,
neurological back pain, when administered in doses lower than
those prescribed for depression. The researcher identifies 3 wellknown, anti-depressive drugs which might have this positive sideeffect, and labels them Drug A, Drug B and Drug C. The
researcher then recruits a group of 60 individuals with a similar
level of back pain and randomly assigns them to one of three
groups - Drug A, Drug B or Drug C treatment groups - and
prescribes the relevant drug for a 4 week period. At the end of
the 4 week period, the researcher asks the participants to rate
their back pain on a scale of 1 to 10, with 10 indicating the
greatest level of pain. The researcher wishes to compare the
levels of pain experienced by the different groups at the end of
the drug treatment period.
Identify the appropriate statistic
• A medical researcher has heard anecdotal evidence that certain antidepressive drugs can have the positive side-effect of lowering
neurological pain in those individuals with chronic, neurological back
pain, when administered in doses lower than those prescribed for
depression. The researcher identifies 3 well-known, anti-depressive
drugs which might have this positive side-effect, and labels them Drug
A, Drug B and Drug C. The researcher then recruits a group of 60
individuals with a similar level of back pain and randomly assigns them
to one of three groups - Drug A, Drug B or Drug C treatment groups and prescribes the relevant drug for a 4 week period. At the end of the 4
week period, the researcher asks the participants to rate their back pain
on a scale of 1 to 10, with 10 indicating the greatest level of pain. The
researcher wishes to compare the levels of pain experienced by the
different groups at the end of the drug treatment period.
– Kruskal-Wallis test
Identify the appropriate statistic
• A researcher studied the relation between
psychotherapists’ degree of empathy and
their patients’ satisfaction with therapy
Identify the appropriate statistic
• A researcher studied the relation between
psychotherapists’ degree of empathy and
their patients’ satisfaction with therapy
– Correlation
Identify the appropriate statistic
• A researcher wants to examine whether music (“no
music", "classical music" and "dance music“) has an effect
on the perceived psychological effort required to perform
an exercise session. The researcher recruited 12 runners
who each ran three times on a treadmill for 30 minutes.
For consistency, the treadmill speed was the same for all
three runs. In a random order, each subject ran: (a)
listening to no music at all; (b) listening to classical music;
and (c) listening to dance music. At the end of each run,
subjects were asked to record how hard the running
session felt on a scale of 1 to 10, with 1 being easy and 10
extremely hard
Identify the appropriate statistic
• A researcher wants to examine whether music (“no music",
"classical music" and "dance music“) has an effect on the
perceived psychological effort required to perform an
exercise session. The researcher recruited 12 runners who
each ran three times on a treadmill for 30 minutes. For
consistency, the treadmill speed was the same for all three
runs. In a random order, each subject ran: (a) listening to no
music at all; (b) listening to classical music; and (c) listening
to dance music. At the end of each run, subjects were
asked to record how hard the running session felt on a
scale of 1 to 10, with 1 being easy and 10 extremely hard
– Friedman test
Identify the appropriate statistic
• A director of a small psychotherapy clinic
is wondering whether there is any
difference in the use of the clinic during
different seasons o fthe year. Last year,
there were 28 new clients in the winter, 33
in the spring, 16 in the summer, and 52 in
the fall. On the basis of last year’s data,
should the director conclude that seasons
makes a difference?
Identify the appropriate statistic
• A director of a small psychotherapy clinic
is wondering whether there is any
difference in the use of the clinic during
different seasons o fthe year. Last year,
there were 28 new clients in the winter, 33
in the spring, 16 in the summer, and 52 in
the fall. On the basis of last year’s data,
should the director conclude that seasons
makes a difference?
– Chi-square goodness of fit
Identify the appropriate statistic
• A pain researcher is interested in finding methods to
reduce lower back pain in individuals without having
to use drugs. The researcher thinks that having
acupuncture in the lower back might reduce back
pain. To investigate this, the researcher recruits 25
participants to their study. At the beginning of the
study, the researcher asks the participants to rate
their back pain on a scale of 1 to 10, with 10
indicating the greatest level of pain. After 4 weeks of
twice weekly acupuncture the participants are asked
again to indicate their level of back pain on a scale
of 1 to 10, with 10 indicating the greatest level of
pain. The researcher wishes to understand whether
the participants' pain levels changed after they had
undergone the acupuncture
Identify the appropriate statistic
• A pain researcher is interested in finding methods to
reduce lower back pain in individuals without having to
use drugs. The researcher thinks that having
acupuncture in the lower back might reduce back pain.
To investigate this, the researcher recruits 25
participants to their study. At the beginning of the study,
the researcher asks the participants to rate their back
pain on a scale of 1 to 10, with 10 indicating the greatest
level of pain. After 4 weeks of twice weekly acupuncture
the participants are asked again to indicate their level of
back pain on a scale of 1 to 10, with 10 indicating the
greatest level of pain. The researcher wishes to
understand whether the participants' pain levels changed
after they had undergone the acupuncture
– Wilcoxon signed-rank test
Identify the appropriate statistic
• Researchers mailed a survey to a random
sample of physicians. Half were offered $1
if they would return the questionnaire this
was the experimental group); the other
half served as a control group. The point
of the study was to see if even a small
incentive would increase the return rate for
physicians surveys
Identify the appropriate statistic
• Researchers mailed a survey to a random
sample of physicians. Half were offered $1
if they would return the questionnaire this
was the experimental group); the other
half served as a control group. The point
of the study was to see if even a small
incentive would increase the return rate for
physicians surveys
– Chi-square tests of independence
Identify the appropriate statistic
• Van Prooijen and colleagues (2004)
carried out a series of studies focusing on
the effect of belongingness and being able
to voice one’s opinion about a decision on
a person’s satisfaction with the decision
making process. The researchers
measured procedural satisfaction by
asking the students to rate how satisfied
they were with the way they were treated
by the other people on their team.
Identify the appropriate statistic
• Van Prooijen and colleagues (2004) carried out
a series of studies focusing on the effect of
belongingness and being able to voice one’s
opinion about a decision on a person’s
satisfaction with the decision making process.
The researchers measured procedural
satisfaction by asking the students to rate how
satisfied they were with the way they were
treated by the other people on their team.
– Factorial ANOVA
Identify the appropriate statistic
• The effectiveness of advertising for two
rival products (Brand X and Y) was carried
out at a local shopping centre. Participants
were shown ads for two brands of coffee,
which they then rated on the overall
likelihood of them buying the product (out
of 10, with 10 being “definitely going to buy
the product”). Half of the participants gave
ratings for one of the products, the other
half gave ratings for the other product
Identify the appropriate statistic
• The effectiveness of advertising for two rival
products (Brand X and Y) was carried out at a
local shopping centre. Participants were shown
ads for two brands of coffee, which they then
rated on the overall likelihood of them buying the
product (out of 10, with 10 being “definitely going
to buy the product”). Half of the participants gave
ratings for one of the products, the other half
gave ratings for the other product
– Mann-Whitney test
Some humour
http://www.youtube.com/watch?v=JS9GmU5hr5w