Question

Some researchers claim that herbal supplements like ginseng
enhance human memory. To test this claim, a researcher selects a
sample of *n*=30 college students. Each student is given a
ginseng supplement daily for six weeks and then all of the
participants are given a standard memory test. For the population,
scores on the test are normally distributed with μ=80 and σ=20. The
sample of *n*=30 students had a mean memory score of
*M*=85.

a) Are these data sufficient to show
that ginseng has a significant effect on memory? Use a two-tailed
z-test with an alpha level of *α=* .05

b) Compute Cohen’s *d* for this
study and interpret the size of the effect

Answer #1

Some researchers claim that herbal supplements such as ginseng
or ginkgo biloba enhance human memory. To test this claim, a
researcher selects a sample of n = 25 college students. Each
student is given a ginkgo biloba supplement daily for six weeks and
then all the participants are given a standardized memory test. For
the population, scores on the test are normally distributed with m
= 70 and s = 15. The sample of n = 25 students had a...

Some researchers claim that herbal supplements such as ginseng
or ginkgo biloba enhance human memory. To test this claim, a
researcher selects a sample of n = 28 college students. Each
student is given a ginkgo biloba supplement daily for 6 weeks and
then all of the participants are given a standardized memory test.
Scores on the standardized test are μ = 80 and standard
deviation of 15. The sample of 28 students had a mean score of M =...

Some researchers claim that herbal supplements such as ginseng
or ginkgo biloba enhance human memory. To test this claim, a
researcher selects a sample of n = 28 college students. Each
student is given a ginkgo biloba supplement daily for 6 weeks and
then all of the participants are given a standardized memory test.
Scores on the standardized test are μ = 80 and standard deviation
of 15. The sample of 28 students had a mean score of M =...

Some researchers claim that herbal supplements improve human
memory. To test this claim, a researcher selects a sample of n = 25
college students. Each student is given herbal supplements daily
for 6 weeks and then all the participants are given a standardized
memory test. For the population, scores on the tests are normally
distributed with µ = 70 and σ= 20. The sample of n = 25 students
had a mean score of M = 80. Can we conclude...

Some researchers claim that herbal supplements improve human
memory. To test this claim, a researcher selects a sample of n = 25
college students. Each student is given herbal supplements daily
for 6 weeks and then all the participants are given a standardized
memory test. For the population, scores on the tests are normally
distributed with µ = 70 and σ= 15. The sample of n = 25 students
had a mean score of M = 75. Can we conclude...

Research has claimed that sleeping 10 hours a night will enhance
human memory. To test this claim, a researcher selects a sample of
n=25 college students. Each of the 25 students is allowed to sleep
10 hours every night in a sleep lab for 4 weeks. All of the
participants are given a standardized memory test after the 4 week
period. For the population, scores on the standardized memory test
are normally distributed with a μ = 70 and σ...

A researcher is testing the effectiveness of a new herbal
supplement that claims to improve memory performance. A
sample of n = 25 college students is obtained and each student
takes the supplement daily for six week. At the end of
the 6-week period, each student is given a standardized memory test
and the average score for the sample is M = 39. For the
general population of college students, the distribution of test
scores is normal with a mean of µ =...

A nutrition store in the mall is selling "Memory Booster," which
is a concoction of herbs and minerals that is intended to improve
memory performance. To test the effectiveness of the herbal mix, a
researcher obtains a sample of n = 16 people and asks each
person to take the suggested dosage each day for four weeks. At the
end of the four-week period, each individual takes a standardized
memory test. The scores from the sample produce a mean of...

In a study examining the effect of caffeine on response time in
the driving simulator, researchers measured reaction time 30
minutes after participants consumed one 6-ouncee cup of coffee.
Using a driving simulation task, for which the distribution of
reaction time is normal with m=400 and s=40, they obtained a mean
of M=392 for a sample of n=36 participants.
a. Are the data sufficient to conclude that caffeine has a
significant effect on reaction time? Use a two-tailed test with...

A researcher wants to know whether supplements affect how long
vampires can go without requiring human blood. She took one sample
of vampires (n = 13). Half received a placebo first and
the supplement second, while the other half received the supplement
first and the placebo second. She then recorded how many days the
vampires could go without consuming human blood for each condition.
The goal of the study was to see whether there would be any
difference between supplement...

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