MATH225 Week 1 Assignment Evidence, Claims and Study Types (July 2019)

MATH 225 Statistical Reasoning for the Health Sciences

Week 1 Assignment Evidence, Claims and Study Types

Question A study was performed with a random sample of 5 people from a certain city. What population would be appropriate for generalizing conclusions from the study, assuming the data collection methods used did not introduce biases?

The conclusions should be restricted to only the city that was sampled.

The conclusions are generalizable to all people on Earth.

The conclusions are generalizable to all people in the country.

The conclusions apply only to the sample.

The conclusions apply to people in any city.

Question In the description of the following experiment, determine the experimental factor. During a study testing a new vaccine for Zika virus, the research team grouped the volunteers enrolled for the test into Group A and Group B. Group A received an inert drug (placebo) while Group B received the vaccine.

whether or not a person contracts the Zika virus

the effectiveness of the new vaccine

the drug received by each group

the group receiving the new vaccine

Question In a psychological study aimed at testing a medicine for reducing stress levels, the researcher grouped the participants into 2 groups and gave the stress-reduction pill to one group and a placebo pill to another group. In the description of the above situation, determine the experimental group.

The group that received the stress-reduction pill is the experimental group.

The group that received the placebo pill is the experimental group.

Both the groups are experimental groups.

Neither group is an experimental group.

Question A researcher is planning to conduct a study of the effectiveness of an herbal tea for short term memory. The experiment will involve people playing a short memory game multiple times after taking either an ordinary tea or the herbal tea. Assume both the teas look alike. Is informing the participants if their tea is ordinary or herbal a good experimental design? Use your best judgement.

No

Yes

Design of Experiments

Components of Experimental Design

In a designed experiment, the researchers deliberately control some factors of the units that are being studied. Typically, the objective of the research is to determine the effect of the variation of one or more of the factors being controlled on the response variables that are being measured.

Often, there is a single factor that is controlled, which has multiple possible values. In many studies, the factor has the form of a treatment applied to the individual units, so sometimes the experimental factor is also called a treatment. Some examples of kinds experimental factors are

• the medication used to treat a medical condition

• the fertilizer used for growing a crop

• the method used to construct a widget

Typically, the research is interested in comparing the effectiveness of new values for the experimental factor with an existing standard value. A control group is included in the study to provide a reference point for having no treatment or for using the common or reference value of the experimental factor. In the situations given above, the experimental factor for the control group would be

• a placebo, or inert treatment, or an existing treatment that is already used

• no fertilizer or the currently used fertilizer

• the current process used to construct the widget

When the experimental units are people, applying treatments that should be inert can actually have effects. This is known as the placebo effect. So the control groups for studies that involve people getting treatments should always be treated the same way as the other groups. If the experimental treatment involves taking a pill, the control group should also be given a pill that is inert.

This also raises a second issue with people involved in studies. The key is that no person who can affect the outcome of a study show know which experimental units have been given which treatments. This is called blinding. In a single blind study, the people receiving the treatments do not know what treatment they are getting. This is to counteract the placebo effect.

In a double blind study, neither the people receiving the treatments nor the researchers know which units receive which treatments until after the experiment is complete and the data has been collected. A double blind study is needed when the researchers can affect the outcomes either intentionally or unintentionally. Double blinding is commonly used in psychological studies and medical studies.

Identify the Treatment

Question

A biology student is performing an experiment to examine the effect of soil moisture on germination time for soy beans. He plants 200 randomly selected soy bean seeds in containers that are prepared as consistently as possible. The containers are all placed under a controlled grow light. The plantings are then randomly divided into four groups. One group receives no water, one group receives 10 mL of water per day, one group receives 20 mL of water per day, and the last group receives 30 mL of water per day. Identify the experimental factor.

Question

In the description of the following experiment, determine the experimental factor. A research team is testing a paste form of a drug to alleviate inflammation. Participants are grouped into Team A and Team B. Team A receives the paste form of the drug. Team B receives a similar paste with no active ingredients.

Team A and Team B

the kind of paste received

the paste with the active ingredient

whether or not the paste helps the inflammation

Question To test the effectiveness of a drug proposed to relieve symptoms of depression, psychiatrists recruited volunteers for clinical tests. All of the volunteers were diagnosed with symptoms of depression. The psychiatrists provided the drug to the first group and a sugar pill to the second group. In the description of the above situation, determine the experimental group.

The group that received the drug is the experimental group.

The group that received the sugar pill is the experimental group.

Neither group is an experimental group.

Both the groups are experimental groups.

Question In the description of the following experiment, determine the experimental factor. A research team is testing a product that will minimize wrinkles among older adults. Volunteers in the age group of 40 to 45 are included in the research. The research team gives a cream to be applied on the face to one group and a placebo cream to the other group.

the average number of wrinkles in each group

the group receiving the active cream

the type of cream given to each group

the average reduction in wrinkles for each group

Question In a study to add a new feature to a software program, the programmer introduced two categories, men and women, in the survey she conducted. Is the study observational or experimental? If it is an experiment, what is the controlled factor?

The study is an experiment. The controlled factor is the feature to be added in the software.

The study is an experiment. The controlled factor is the category, men or women.

The study is an observational study.

The study is an experiment. The controlled factor is the survey.

Question An energy drink manufacturer wants to find out the effect of different amounts of their product on the maximum anaerobic power level for rowers. Would an experimental or observational study design be more appropriate?

An experimental study should be used with the maximum anaerobic power as the controlled factor.

An experimental study should be used with the amount of the drink consumed as the controlled factor.

An observational study should be used because the amount of the drink consumed cannot be controlled.

An observational study should be used because the maximum anaerobic power cannot be directly controlled.

Question A biology student is interested in the relationship between temperature and germination time for soy beans. The student gets sample seeds from multiple sources and randomly selects 180 seeds from them. Then he sets up three growing stations, one at 20?C, one at 15?C, and one at 25?C. He divides the seeds into three groups of 60 and plants the seeds from each group in a growing station. He records the germination time for each seed.

Is this an observational study or an experiment? If it is an experiment, what is the controlled factor?

The study is an observational study.

The study is an experiment. The controlled factor is the germination time.

The study is an experiment. The controlled factor is the temperature.

The study is an experiment. The controlled factor is the seeds.

Observational and Experimental Studies

There are two primary ways to collect data from a new sample: an observational study and an experimental study. Both of these methods involve choosing a sample of individuals from the population and recording the value of one or more variables for each individual. However, there are some differences.

In an observational study, no attempt is made to control any aspect of the individuals in the sample. The sample is chosen using an appropriate process, and the variables of interest are recorded for each individual. This kind of study is typically used when it is difficult, unethical, or impossible to control factors in the sample. An observational study is also commonly used when there are no factors that would need to be controlled. Here are a few examples where an observational study would be used:

• A study on the relationship between smoking and the risk of lung cancer

• A study on the relationship between premature birth and early reading skills

• A survey of the opinions of residents on a proposed addition to the local school

In an experimental study, the researchers attempt to control one or more aspects of the individuals in the sample. The individuals in the sample will be randomly divided into multiple groups or cases. Then the controlled factors will be set for each of the groups as chosen by the researchers. This may be more clear with a few examples of experimental studies:

• Researchers randomly assign individuals to three groups. One group listens to no music, one group listens to a top 40 channel from a streaming service, and one group listens to individually selected music. The researchers then give the subjects a cognitive test.

• An agricultural agency divides 100 plots into two groups. One group receives no pesticides and the other group receives pesticide treatments. The crop yields of each plot are measured at the end of the season.

Observational or Experimental?

Question A large manufacturing firm is interested in the effect of the temperature of the manufacturing floor on worker productivity. Over the course of a year, the firm randomly samples its 103 sites and records the temperature and the quantity of items produced on that day. Is this an experiment or an observational study?

Question A study was conducted among school students on the relationship between getting up late and getting to school late. Is this an example of an observational study or experimental study? If it is an experiment, what is the controlled factor?

The study is an observational study.

The study is an experiment. The controlled factor is getting up late.

The study is an experiment. The controlled factor is getting to school late.

The study is an experiment. The controlled factor is the school students.

Question A consumer research company is interested in determining if a certain company’s new refrigerator model is more efficient than the older model. Researchers decide to investigate the claim that the new model uses 10% less electricity than the older model for the same cooling load. Which data collection method is appropriate? Select only one answer choice.

The company should obtain random samples of people who own each model and measure the electricity used over one month for each refrigerator.

The company should obtain random samples of each model, place them in similar conditions, fill them with the same amount of water bottles, and monitor their electrical usage over one month.

The company should get a random sample of the new model, place them all in similar conditions, fill them with the same number of water bottles, and monitor their electrical usage over one month.

The company should obtain one new model and one old model, place them both in the same room, fill them with the same number of water bottles, and monitor their electrical usage over one month.

Question A statistics student has obtained a sample by surveying all the students in his class. What group can the results of the survey be generalized to?

The conclusions should apply to all students at the college.

The conclusions should apply to students at any college.

The conclusions should apply only to the sample.

The conclusions should apply to all people.

Question A consumer research company is interested in determining if a certain company’s new refrigerator model is more efficient than the older model. What should the researchers do first?

Write a claim about the efficiency of the new model that can be tested.

Choose a random sample of the new models to perform testing.

Make some initial conclusions about the efficiency of the new model.

Make some initial conclusions about the efficiency of the old model.

Question A biologist wants to study the effect of vitamin D enriched food on the weight of adult mice. Would an experimental or observational study design be more appropriate?

An observational study should be used because the type of food consumed cannot be controlled.

An observational study should be used because the weight of adult mice cannot be controlled.

An experimental study should be used where the food consumed is the controlled factor.

An experimental study should be used where the weight of adult mice is the controlled factor.

Question In a survey conducted to find out the feedback of a sports program organized in a club, the organizers asked the respondents to classify their feedback as good, fair, poor, and bad. Is the study observational or experimental? If it is an experiment, what is the controlled factor?

The study is an observational study.

The study is an experiment. The controlled factor is the feedback.

The study is an experiment. The controlled factor is the ratings.

The study is an experiment. The controlled factor is the respondents.

Question A pharmaceutical company conducted an experiment to test a drug for controlling diabetes. The company enrolled participants for the experiment and divided them into 2 groups. One group received an inert drug and the other group received the diabetes control drug. In the description of the above experiment, determine the experimental group.

The group that received the inert drug is the experimental group

The group that received the diabetic control drug is the experimental group

Both the groups are experimental groups

Neither group is an experimental group

Question In the description of the following experiment, determine the experimental factor. A team of physicians testing a new liquid drug taken using an inhaler for treating colds gave the drug to one group of volunteers enrolled for the test. They gave the other group water using the same kind of inhaler.

whether or not the subject’s cold was cured

the type of liquid received by each group

the new liquid drug

all of the people in the study

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