Statistics Ch 5-7

An experiment is being conducted to determine the optimal fertilizer amount per plant for a particular variety of corn to maximize yield. Corn was planted in small plots randomly assigned to duplicate planting rates of 8,000, 10,000, and 12,000 plants per acre. Fertilizer was applied to each plot at randomized rates that duplicated 100, 150, and 200 pounds per acre. How many treatments are being used in this experiment?

9 There are three levels for planting rate and three levels for fertilizer amount, so these combine to nine treatments for the experiment.

An experiment is being conducted to determine the optimal fertilizer amount per plant for a particular variety of corn to maximize yield. Corn was planted in small plots randomly assigned to duplicate planting rates of 8,000, 10,000, and 12,000 plants per acre. Fertilizer was applied to each plot at randomized rates that duplicated 100, 150, and 200 pounds per acre. If we want to use 10 plots per treatment, how many plots will be needed in this experiment?

90 There are three levels for planting rate and three levels for fertilizer amount, so these combine to nine treatments for the experiment. For 10 plots per treatment, we'll need 9 x 10 = 90 plots.

In an observational study, participants were asked how often they ate apples. Their "bad" (LDL) cholesterol level was also measured. Those who ate two or more apples per day had a significantly lower "bad" cholesterol level than those who didn't. But those who eat a lot of apples may also eat half their plate in fruits and vegetables. What term can we use to describe the variable "whether they eat half their plate in fruits and vegetables"?

A confounded variable

To test the effectiveness of using a dab of honey to prevent infection in a cut, parents of children in a childcare facility were instructed to wash the wounds of their children with soap and water and then place a dab of honey on the cut. Each cut was then monitored for infection. At the end of the study, the percentage of the twenty eight children who had cuts that became infected was computed. What is a necessary feature that this experiment is lacking?

A control/comparison group

Students in an introductory statistics course can take each exam twice. One student got a 66 on the first attempt and a 92 on the second. Which of the following statements is true?

A. This improvement is statistically significant

A vaccine for preventing shingles (a painful, blistering skin rash caused by a virus) in older adults was tested on a group of adults aged 50 to 70 years old. Half of the adults were randomly assigned to receive the vaccine and the other half were assigned to receive a placebo. For the next 10 years each adult was examined to see whether he/she contracted shingles. What type of study is this?

An experiment

Students in an introductory statistics course can take each exam twice. One student got a 71 on the first attempt and a 73 on the second. Which of the following statements is true?

B. This improvement is not statistically significant

A vaccine for preventing shingles (a painful, blistering skin rash caused by the chicken pox virus) in older adults was tested on a group of 100 adults aged 50 to 70 years old. Half of the adults were randomly assigned to receive the vaccine and the other half were assigned to receive a placebo. For the next 10 years each adult was examined to see whether he/she contracted shingles. If the difference between the shingles rate for the vaccine group and the shingles rate for the placebo group is "due to chance", what can we conclude?

B. This vaccine does not prevent shingles

An experiment is being conducted to determine the optimal fertilizer amount per plant for a particular variety of corn to maximize yield. Corn was planted in small plots randomly assigned to duplicate planting rates of 8,000, 10,000, and 12,000 plants per acre. Fertilizer was applied to each plot at randomized rates that duplicated 100, 150, and 200 pounds per acre. We have 90 plots available to use for the experiment. Of the following sources of possible concern, which is the most troubling possibility with this experiment?

Confounding

An experiment is being conducted to determine the optimal fertilizer amount per plant for a particular variety of corn to maximize yield. Corn was planted in small plots randomly assigned to duplicate planting rates of 8,000, 10,000, and 12,000 plants per acre. Fertilizer was applied to each plot at randomized rates that duplicated 100, 150, and 200 pounds per acre. We have 90 plots available to use for the experiment. To get the best possible information from the experiment, we'll need to

Make sure all plots get similar water

An experiment is being conducted to determine the most effective dose of a new treatment for an illness that impacts cows. The drug was given to the cows with doses of 30 ml, 60 ml, and 90 ml. There are 75 animals in the study. To get the best possible information from the experiment, we'll need to

Make sure all the animals are cared for in the same way.

Institutional review boards (IRBs) are tasked with reviewing all studies involving human subjects to protect their rights and welfare. One criticism of the IRB process is that when they are overworked they may be tempted to categorize some studies as ______ risk when they shouldn't be.

Minimal

A study is being proposed to compare the benefits on reducing blood pressure of jogging versus walking. Fifty adults aged 40 to 55 with high blood pressure are to be divided into two groups by tossing a coin. If the coin is heads, the adult will be assigned to jog two miles three times a week; otherwise the adult will be assigned to walk three miles three times a week. At the end of three months, the reduction in blood pressure will be compared for the two groups. Is this experiment double-blind?

No It is impossible to blind subjects as to whether they job or walk.

Fifteen adults undergoing chemotherapy were randomly assigned to listen to music during their four treatments. Data were collected on the degree of nausea before, during and after each treatment. The same data were also collected on a group of randomly assigned adults who did not listen to music during their four chemo treatments. Is this experiment double-blind?

No This experiment cannot be double-blind because the subjects have to know that they're listening to music.

Some students attend an optional pre-test study session and others do not. Comparing these two groups on performance of the exam would be an example of an experiment.

No, because there isn't random assignment.

Students in an introductory statistics course can take each exam twice. Some do, some do not. If we want to assess whether taking the test a second time results in better grades, do we have a valid experiment?

No, because there isn't random assignment.

To test the effectiveness of using a dab of honey to prevent infection in a cut, parents of children in a childcare facility were instructed to wash the wounds of their children with soap and water and then place a dab of honey on the cut. Each cut was then monitored for infection. At the end of the study, the percentage of the twenty eight children who had cuts that became infected was computed. What is a necessary feature that this experiment is lacking?

Randomization

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

Randomization

A study to investigate a new potential treatment for Alzheimer's disease used a special insulin nasal spray to get sugar to the brain in less than 30 minutes' time. The 104 volunteers who participated in the study either had Alzheimer's or pre-Alzheimer's memory problems. Those with Alzheimer's were randomly assigned to either receive a daily dose of insulin or to receive a placebo. Those with pre-Alzheimer's were also randomly assigned to the two treatments. What type of study is this?

Randomized block experiment

To test the effectiveness of using a dab of honey to prevent infection in a cut, parents of children in a childcare facility were instructed to wash the wounds of their children with soap and water and then place a dab of honey on the cut. Each cut was then monitored for infection. At the end of the study, the percentage of the twenty eight children who had cuts that became infected was computed. What is a necessary feature that this study has?

Replication

Researcher A and Researcher B both observe an effect of a 2.5 point drop in blood pressure due to a new medication. Researcher A's results are not significant but Researcher B's results are. Why?

Researcher B has a larger sample size.

A study is being proposed to compare the benefits of jogging versus walking on reducing blood pressure. Sixty adults aged 40 to 55 with high blood pressure are to be divided into groups. Some will be assigned to jog two miles once, twice, or three times a week; others will be assigned to walk three miles once, twice, or three times a week. At the end of three months, the reduction in blood pressure will be compared. What are the response variable(s) in this study?

The amount of reduction in blood pressure

Which of the following is not a potential cause of bias in an experiment?

The results are not what the researcher expected.

A study is being proposed to compare the benefits of jogging versus walking on reducing blood pressure. Sixty adults aged 40 to 55 with high blood pressure are to be divided into groups. Some will be assigned to jog two miles once, twice, or three times a week; others will be assigned to walk three miles once, twice, or three times a week. At the end of three months, the reduction in blood pressure will be compared. What are the treatments in this study?

The six combinations of walking/jogging with frequency once, twice, or three times a week.

Researchers sometimes try all of the following to lessen the barriers of informed consent except: _____.

They may list all possible risks in a long detailed form.

One day in August, the temperature was 103 degrees Fahrenheit. Ten minutes later the temperature was 104 degrees. Which of the following statements is true?

This increase in temperature is not statistically significant

To test the effectiveness of using a dab of honey to prevent infection in a cut, parents of children in a childcare facility were instructed to wash the wounds of their children with soap and water and then place a dab of honey on the cut. Each cut was then monitored for infection. At the end of the study, the percentage of the twenty eight children who had cuts that became infected was computed. Which of the following statements is false?

This is a completely randomized experiment

A vaccine for preventing shingles (a painful, blistering skin rash caused by the chicken pox virus) in older adults was tested on a group of 100 adults aged 50 to 70 years old. Half of the adults were randomly assigned to receive the vaccine and the other half were assigned to receive a placebo. For the next 10 years each adult was examined to see whether he/she contracted shingles. If the difference between the shingles rate for the vaccine group and the shingles rate for the placebo group is bigger than we expect "due to chance", what can we conclude?

This vaccine prevents shingles.

Fifteen adults undergoing chemotherapy were randomly assigned to listen to music during their four chemo treatments. For each treatment, data were collected on the degree of nausea before, during and after the chemo. The same data were also collected on another group of fifteen adults who were randomly assigned not listen to music during their therapy for their four chemo treatments. What is the explanatory variable of primary interest?

Whether subject received music therapy during chemo treatment

Confidentiality is _____.

an agreement to keep identifying information private

The Minnesota Study of Twins Reared Apart investigated whether attributes of twins are related to heredity or the influence of family environment. The researchers compared intense psychological and physiological assessment results of 56 pairs of identical twins reared apart and several hundred identical twins reared together. (Data from EESEE.) What type of study is this?

an observational study

A group of individuals known to be similar in some way that affects the response before an experiment begins is called a(n) _____.

block

An observed event that would rarely occur by ___________ is called statistically significant.

chance

A good observational study measures and adjusts for _______ variables.

confounding

If you consent to a behavioral or social science experiment, you could actually be misled about the study or the intent of the study because _____ is allowed.

deception

The APA allows deception only when all of the following are true, except: _____.

deception makes the study more interesting

When experiments are not fully realistic, they are _____ to generalize into a bigger population.

difficult

A researcher wants to know if taking increasing amounts of ginkgo biloba will result in increased capacities of memory ability for different students. They administer it to the students in doses of 250 milligrams, 500 milligrams, and 1000 milligrams. The __________ variable in this study is the amount of ginkgo biloba taken by the students.

explanatory

In a study to determine whether surgery or chemotherapy results in higher survival rates for a certain type of cancer, whether or not the patient survived is one variable, and whether they received surgery or chemotherapy is the other. Treatment type is the ________ variable here.

explanatory

Hospital employees are frequently invited to participate in studies going on at their institutions and are often compensated for their time. These studies are not generalizable to all people because _____.

hospital employees are not representative of all people in general.

The _____ review board reviews all planned studies to protect the subjects from possible harm.

institutional

Once a study begins, the institutional review board _____.

monitors the progress of the study at least once a year Many studies are required to maintain contact with the IRB and give updates at least once a year.

The APA allows deception if it is _____ to the study.

necessary

In assessing statistical significance, it is best to know the magnitude of the observed effect and the _____________.

number of subjects.

An experiment is being conducted to determine the optimal fertilizer amount per plant for a particular variety of corn to maximize yield. Corn was planted in small plots randomly assigned to duplicate planting rates of 8,000, 10,000, and 12,000 plants per acre. Fertilizer was applied to each plot at randomized rates that duplicated 100, 150, and 200 pounds per acre. We have 90 plots available to use for the experiment. To get the best possible information from the experiment, we'll need to use a(n) _____ treatment.

placebo

Sham surgeries have been approved and used as a _____ group in recent clinical trials.

placebo

The response to a dummy treatment is called the ________ effect .

placebo

A matched pairs design can give more _____ results than a completely randomized design.

precise

A large clinical trial used over 8,000 subjects for its Phase III trial of a new cholesterol medicine. It was found that cholesterol was significantly reduced in the treatment group. As long as the subjects are _____ of the target population and the setting was realistic, the results of this study are generalizable because it is a clinical trial.

representative

Experimenters must tell subjects the nature and purpose of the study and outline possible _____.

risks

In experimental design, randomization produces groups of subjects that ____________.

should be similar in all respects before the treatment is applied.

A treadmill company is conducting a study to determine if running on the treadmill 30 minutes per day at lunch will help with cardiovascular health. One hundred employees of an investment firm in a posh high rise were chosen for the study. At the end of three months, their cardiovascular health was evaluated and found to be significantly improved. The results of this study cannot be generalized to all people because _____.

the 100 employees of an investment firm in a posh high rise are not representative of all people.

Researchers want to know if taking increasing amounts of ginkgo biloba will result in increased capacities of memory ability for different students. They administer it to the students in doses of 250 milligrams, 500 milligrams, and 1000 milligrams daily, for one month. At the end of the month the students were asked to complete a memory test and researchers recorded the amount of points each student scored. The explanatory variable in this study is ______________.

the amount of ginkgo biloba

A treadmill company is conducting a study to determine if running on the treadmill 30 minutes per day at lunch will help with cardiovascular health. One hundred employees of a busy urban hospital were chosen for the study. Their cardiovascular health at the end of three months was evaluated and found to be significantly improved. The results of this study cannot be generalized to all people because _____.

the subjects are not representative of the general public.

Some ethical difficulties may exist in medical treatments because _____.

they could do harm or good to the subject

Subjects in many behavior experiments are asked to consent on the basis of _____ information.

vague