Intro to Stat 1.6

Treatment

Any combination of the values of the factors​ (explanatory variables)

Confounding variable

Explanatory variable that was considered in a study whose effect cannot be distinguished from a second explanatory variable in the study

A gambler wanted to compare two types of poker strategies. One type is playing tight and the other is a loose style of play. It is a common belief that playing tight will win more pots. This belief is tested by having 10 poker players use each type of strategy in a game and comparing the number of pots won under each method of play. A coin flip was used to determine which type of poker strategy each player would follow first. Results indicated that there was no difference in the two types of strategy. What type of experimental design is​ this?

​Matched-pairs design

Control group

Serves as a baseline treatment that can be used to compare to other treatments

Single-blind

Experimental unit (or subject) does not know which treatment he or she is receiving

Placebo

An innocuous medication, such as a sugar tablet, that looks, tastes, and smells like the experimental medication

To research the claim that green tea lowers LDL​ (so-called bad)​ cholesterol, you ask a random sample of individuals to divulge whether they are regular green tea users or not. You also obtain their LDL cholesterol levels.​ Finally, you compare the LDL cholesterol levels of the green tea drinkers to those of the​ non-green tea drinkers.What factors might you attempt to control in this​ experiment?

- Diet - Exercise

To research the claim that green tea lowers LDL​ (so-called bad)​ cholesterol, you ask a random sample of individuals to divulge whether they are regular green tea users or not. You also obtain their LDL cholesterol levels.​ Finally, you compare the LDL cholesterol levels of the green tea drinkers to those of the​ non-green tea drinkers. Name some lurking variables that might exist in the study. Select all that apply.

- Genetics - Exercise - Gender - Diet - Age

What are the two ways to control the factors?

1. Set the level of the factor at one value throughout the experiment (if you are not interested in its effect on the response variable) 2. Set the level of a factor at various levels (if you are interested in its effect on the response variable). The combinations of the levels of all varied factors constitute the treatments in the experiment

Researchers wanted to test the effectiveness of a new drug therapy for treating patients with diabetes. To do​ this, they identified 60 patients with a diagnosis of diabetes. Patients were randomly assigned to one of three treatment groups. Twenty patients were randomly assigned to receive the new drug​ therapy, another 20 received the older drug​ therapy, and the final 20 received a placebo therapy. To measure the effectiveness of the​ treatment, researchers scored each patient on a standardized rating scale for diabetes. After collecting and comparing the scores for the three treatment​ groups, the researchers concluded that the new drug therapy is significantly more effective than both the older drug therapy and the placebo therapy in the treatment of diabetes. What is the population being​ studied?

All patients with a diagnosis of diabetes

Matched-pairs design

An experimental design in which the experimental units are paired up. The pairs are selected so that they are related in some way (that is, the same person before and after a treatment, twins, husband and wife, same geographical location, and so on). (Boxy diagram)

To determine if topiramate is an effective treatment for alcohol​ dependence, researchers conducted a​ 14-week trial of 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. In this​ doubleblind, randomized,​ placebo-controlled experiment, subjects were randomly given either 300 milligrams​ (mg) of topiramate​ (183 subjects) or a placebo​ (188 subjects)​ daily, along with a weekly compliance enhancement intervention. The variable used to determine the effectiveness of the treatment was​ self-reported percentage of heavy drinking days. Results indicated that topiramate was more effective than placebo at reducing the percentage of heavy drinking days. The researchers concluded that topiramate is a promising treatment for alcohol dependence. What are the​ treatments?

300 mg of topiramate or a placebo​ daily, and a weekly compliance enhancement intervention

Experiment

A controlled study conducted to determine the effect of varying one or more explanatory variables or factors has on a response variable.

Experimental unit (or subject)

A person, object or some other well-defined item upon which a treatment is applied

Inferential statistics

A process in which generalizations about a population are made on the basis of results obtained from a sample

Factor

A variable whose effect on the response variable is to be assessed by the experimenter

To research the claim that green tea lowers LDL​ (so-called bad)​ cholesterol, you ask a random sample of individuals to divulge whether they are regular green tea users or not. You also obtain their LDL cholesterol levels.​ Finally, you compare the LDL cholesterol levels of the green tea drinkers to those of the​ non-green tea drinkers. Suppose you assigned 40 subjects to each of the three treatment groups. In​ addition, you decided to control the variable exercise by having each subject perform 150 minutes of cardiovascular exercise each week by walking on a treadmill.​ However, the 40 subjects in the placebo group decided they did not want to walk on the treadmill and skipped the weekly exercise. Explain how exercise is now a confounding variable.

Any difference in the change in the 'response variable' cannot be attributed to the 'treatment level.' It may be the 'exercise' that caused the change in the 'response variable'

Researchers wanted to test the effectiveness of a new drug therapy for treating patients with diabetes. To do​ this, they identified 60 patients with a diagnosis of diabetes. Patients were randomly assigned to one of three treatment groups. Twenty patients were randomly assigned to receive the new drug​ therapy, another 20 received the older drug​ therapy, and the final 20 received a placebo therapy. To measure the effectiveness of the​ treatment, researchers scored each patient on a standardized rating scale for diabetes. After collecting and comparing the scores for the three treatment​ groups, the researchers concluded that the new drug therapy is significantly more effective than both the older drug therapy and the placebo therapy in the treatment of diabetes. What type of experimental design is​ this?

Completely randomized design

To research the claim that green tea lowers LDL​ (so-called bad)​ cholesterol, you ask a random sample of individuals to divulge whether they are regular green tea users or not. You also obtain their LDL cholesterol levels.​ Finally, you compare the LDL cholesterol levels of the green tea drinkers to those of the​ non-green tea drinkers. Suppose, instead of surveying individuals regarding their​ tea-drinking habits, you decide to conduct a designed experiment. You identify 120 volunteers to participate in the study and decide on three levels of the​ treatment: a​ placebo, one cup of green tea​ daily, two cups of green tea daily. The experiment is to run for one year. The response variable will be the change in LDL cholesterol for each subject from the beginning of the study to the end. What type of experimental design is​ this?

Completely randomized design

Completely randomized design

Design in which each experimental unit is randomly assigned to a treatment (Bubbly diagram)

To research the claim that green tea lowers LDL​ (so-called bad)​ cholesterol, you ask a random sample of individuals to divulge whether they are regular green tea users or not. You also obtain their LDL cholesterol levels.​ Finally, you compare the LDL cholesterol levels of the green tea drinkers to those of the​ non-green tea drinkers. Explain how you would use blinding in this experiment.

Do not allow the subjects to know which level of the treatment they are receiving.​ Also, do not allow the​ researcher(s) giving the treatments to know which level of the treatment they are giving. This is a​ double-blind study.

Blocking

Grouping together similar experimental units and then randomly assigning the experimental units within each group to a treatment

Explain the difference between a​ single-blind and a​ double-blind experiment.

In a​ single-blind experiment, the subject does not know which treatment is received. In a​ double-blind experiment, neither the subject nor the researcher in contact with the subject knows which treatment is received.

To determine if topiramate is an effective treatment for alcohol​ dependence, researchers conducted a​ 14-week trial of 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. In this​ doubleblind, randomized,​ placebo-controlled experiment, subjects were randomly given either 300 milligrams​ (mg) of topiramate​ (183 subjects) or a placebo​ (188 subjects)​ daily, along with a weekly compliance enhancement intervention. The variable used to determine the effectiveness of the treatment was​ self-reported percentage of heavy drinking days. Results indicated that topiramate was more effective than placebo at reducing the percentage of heavy drinking days. The researchers concluded that topiramate is a promising treatment for alcohol dependence. What does it mean for the experiment to be​ randomized?

It means that the subjects are randomly assigned to take either the topiramate or the placebo.

A professor wanted to compare two types of teaching styles. One type is by tutorials and the other is giving a lecture. It is a common belief that tutorials result in better retention. This belief is tested by having 10 students learn a topic by each method and then having them take a test on their knowledge of the material that was covered. A coin flip was used to determine which type of teaching method a student would be given first. Results indicated that there was no difference in the two types of presentation. What type of experimental design is​ this?

Matched-pairs design

Double-blind

Neither the experimental unit nor the researcher in contact with the experimental unit knows which treatment the experimental unit is receiving

To determine if topiramate is an effective treatment for alcohol​ dependence, researchers conducted a​ 14-week trial of 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. In this​ doubleblind, randomized,​ placebo-controlled experiment, subjects were randomly given either 300 milligrams​ (mg) of topiramate​ (183 subjects) or a placebo​ (188 subjects)​ daily, along with a weekly compliance enhancement intervention. The variable used to determine the effectiveness of the treatment was​ self-reported percentage of heavy drinking days. Results indicated that topiramate was more effective than placebo at reducing the percentage of heavy drinking days. The researchers concluded that topiramate is a promising treatment for alcohol dependence. What does it mean for the experiment to be​ double-blind? Why do you think it is necessary for the experiment to be​ double-blind? Why do you think it is necessary for the experiment to be​ double-blind?

Neither the subject nor the researcher knows which treatment the subject is receiving. ; The experiment is​ double-blind so that the subjects receiving the medication do not behave differently and so the individual monitoring the subjects does not treat those receiving medication differently from those receiving a placebo.

To determine if topiramate is an effective treatment for alcohol​ dependence, researchers conducted a​ 14-week trial of 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. In this​ doubleblind, randomized,​ placebo-controlled experiment, subjects were randomly given either 300 milligrams​ (mg) of topiramate​ (183 subjects) or a placebo​ (188 subjects)​ daily, along with a weekly compliance enhancement intervention. The variable used to determine the effectiveness of the treatment was​ self-reported percentage of heavy drinking days. Results indicated that topiramate was more effective than placebo at reducing the percentage of heavy drinking days. The researchers concluded that topiramate is a promising treatment for alcohol dependence. What is the response​ variable?

Percentage of heavy drinking days

To research the claim that green tea lowers LDL​ (so-called bad)​ cholesterol, you ask a random sample of individuals to divulge whether they are regular green tea users or not. You also obtain their LDL cholesterol levels.​ Finally, you compare the LDL cholesterol levels of the green tea drinkers to those of the​ non-green tea drinkers. Explain how to use randomization in this experiment. How does randomization neutralize those variables that are not​ controlled?

Randomly assign the 'experimental units' to treatment groups. This will mute the effect of variation attributable to the 'explanatory variables' that are not controlled. Then any difference in the value of the response variable among the different treatment groups is a result of 'differences in the level of the treatment.'

Blinding

Refers to the nondisclosure of the treatment an experimental unit is receiving

What are the 6 steps in designing an experiment?

Step 1. Identify the problem to be solved Step 2. Determine the factors that affect the response variable Step 3. Determine the number of experimental units Step 4. Determine the level of each factor (Control or randomize) Step 5. Conduct the experiment Step 6. Test the claim

Researchers wanted to test the effectiveness of a new drug therapy for treating patients with diabetes. To do​ this, they identified 60 patients with a diagnosis of diabetes. Patients were randomly assigned to one of three treatment groups. Twenty patients were randomly assigned to receive the new drug​ therapy, another 20 received the older drug​ therapy, and the final 20 received a placebo therapy. To measure the effectiveness of the​ treatment, researchers scored each patient on a standardized rating scale for diabetes. After collecting and comparing the scores for the three treatment​ groups, the researchers concluded that the new drug therapy is significantly more effective than both the older drug therapy and the placebo therapy in the treatment of diabetes. Identify the experimental units.

The 60 patients with a diagnosis of diabetes

Confounding

The effect of two factors (explanatory variables on the response variable) cannot be distinguished

To determine if topiramate is an effective treatment for alcohol​ dependence, researchers conducted a​ 14-week trial of 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. In this​ doubleblind, randomized,​ placebo-controlled experiment, subjects were randomly given either 300 milligrams​ (mg) of topiramate​ (183 subjects) or a placebo​ (188 subjects)​ daily, along with a weekly compliance enhancement intervention. The variable used to determine the effectiveness of the treatment was​ self-reported percentage of heavy drinking days. Results indicated that topiramate was more effective than placebo at reducing the percentage of heavy drinking days. The researchers concluded that topiramate is a promising treatment for alcohol dependence. What does it mean for the experiment to be​ placebo-controlled?

The experiment will have a control group that takes a​ placebo, which is a innocuous​ medication, such as a sugar tablet. This control group serves as a baseline treatment that can be used to compare to the group that is actually taking the medication.

To research the claim that green tea lowers LDL​ (so-called bad)​ cholesterol, you ask a random sample of individuals to divulge whether they are regular green tea users or not. You also obtain their LDL cholesterol levels.​ Finally, you compare the LDL cholesterol levels of the green tea drinkers to those of the​ non-green tea drinkers. What is the​ factor? Is it qualitative or​ quantitative?

The factor is 'the amount of green tea daily.' It is 'qualitative.'

A professor wanted to compare two types of teaching styles. One type is by tutorials and the other is giving a lecture. It is a common belief that tutorials result in better retention. This belief is tested by having 10 students learn a topic by each method and then having them take a test on their knowledge of the material that was covered. A coin flip was used to determine which type of teaching method a student would be given first. Results indicated that there was no difference in the two types of presentation. What is the factor that is set to predetermined​ levels? What is the​ treatment?

The factor is the type of presentation. The treatments are by tutorials and giving a lecture.

A gambler wanted to compare two types of poker strategies. One type is playing tight and the other is a loose style of play. It is a common belief that playing tight will win more pots. This belief is tested by having 10 poker players use each type of strategy in a game and comparing the number of pots won under each method of play. A coin flip was used to determine which type of poker strategy each player would follow first. Results indicated that there was no difference in the two types of strategy. What is the factor that is set to predetermined​ levels? What is the​ treatment?

The factor is the type of strategy. The treatments are playing tight and a loose style of play.

Researchers wanted to test the effectiveness of a new drug therapy for treating patients with diabetes. To do​ this, they identified 60 patients with a diagnosis of diabetes. Patients were randomly assigned to one of three treatment groups. Twenty patients were randomly assigned to receive the new drug​ therapy, another 20 received the older drug​ therapy, and the final 20 received a placebo therapy. To measure the effectiveness of the​ treatment, researchers scored each patient on a standardized rating scale for diabetes. After collecting and comparing the scores for the three treatment​ groups, the researchers concluded that the new drug therapy is significantly more effective than both the older drug therapy and the placebo therapy in the treatment of diabetes. What are the​ treatment(s)?

The new drug​ therapy, the older drug​ therapy, and the placebo therapy

A gambler wanted to compare two types of poker strategies. One type is playing tight and the other is a loose style of play. It is a common belief that playing tight will win more pots. This belief is tested by having 10 poker players use each type of strategy in a game and comparing the number of pots won under each method of play. A coin flip was used to determine which type of poker strategy each player would follow first. Results indicated that there was no difference in the two types of strategy. What is the response variable in this​ study?

The number of pots won

A gambler wanted to compare two types of poker strategies. One type is playing tight and the other is a loose style of play. It is a common belief that playing tight will win more pots. This belief is tested by having 10 poker players use each type of strategy in a game and comparing the number of pots won under each method of play. A coin flip was used to determine which type of poker strategy each player would follow first. Results indicated that there was no difference in the two types of strategy. Identify the experimental units.

The poker players

To determine if topiramate is an effective treatment for alcohol​ dependence, researchers conducted a​ 14-week trial of 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. In this​ doubleblind, randomized,​ placebo-controlled experiment, subjects were randomly given either 300 milligrams​ (mg) of topiramate​ (183 subjects) or a placebo​ (188 subjects)​ daily, along with a weekly compliance enhancement intervention. The variable used to determine the effectiveness of the treatment was​ self-reported percentage of heavy drinking days. Results indicated that topiramate was more effective than placebo at reducing the percentage of heavy drinking days. The researchers concluded that topiramate is a promising treatment for alcohol dependence. What is the population for which this study​ applies? What is the​ sample?

The population is all​ 18-65 year olds with alcohol dependence. The sample is 371 men and women aged 18 to 65 years diagnosed with alcohol dependence.

Researchers wanted to test the effectiveness of a new drug therapy for treating patients with diabetes. To do​ this, they identified 60 patients with a diagnosis of diabetes. Patients were randomly assigned to one of three treatment groups. Twenty patients were randomly assigned to receive the new drug​ therapy, another 20 received the older drug​ therapy, and the final 20 received a placebo therapy. To measure the effectiveness of the​ treatment, researchers scored each patient on a standardized rating scale for diabetes. After collecting and comparing the scores for the three treatment​ groups, the researchers concluded that the new drug therapy is significantly more effective than both the older drug therapy and the placebo therapy in the treatment of diabetes. What is the response variable in this​ study?

The score on the standardized rating scale for diabetes

A professor wanted to compare two types of teaching styles. One type is by tutorials and the other is giving a lecture. It is a common belief that tutorials result in better retention. This belief is tested by having 10 students learn a topic by each method and then having them take a test on their knowledge of the material that was covered. A coin flip was used to determine which type of teaching method a student would be given first. Results indicated that there was no difference in the two types of presentation. What is the response variable in this​ study?

The score on the test

When a factor is controlled by setting it to three​ levels, the particular factor is of no interest to the researcher. T/F

The statement is false because a factor that is controlled and set at various levels is a factor of interest to the researcher.

A professor wanted to compare two types of teaching styles. One type is by tutorials and the other is giving a lecture. It is a common belief that tutorials result in better retention. This belief is tested by having 10 students learn a topic by each method and then having them take a test on their knowledge of the material that was covered. A coin flip was used to determine which type of teaching method a student would be given first. Results indicated that there was no difference in the two types of presentation. Identify the experimental units.

The students

To research the claim that green tea lowers LDL​ (so-called bad)​ cholesterol, you ask a random sample of individuals to divulge whether they are regular green tea users or not. You also obtain their LDL cholesterol levels.​ Finally, you compare the LDL cholesterol levels of the green tea drinkers to those of the​ non-green tea drinkers. Explain why this is an observational study.

This is an observational study because there is no intent to manipulate the explanatory​ variable, whether the individual is a green tea drinker or not.

A professor wanted to compare two types of teaching styles. One type is by tutorials and the other is giving a lecture. It is a common belief that tutorials result in better retention. This belief is tested by having 10 students learn a topic by each method and then having them take a test on their knowledge of the material that was covered. A coin flip was used to determine which type of teaching method a student would be given first. Results indicated that there was no difference in the two types of presentation. Why is a coin used to decide the teaching method a student would be given first​?

To eliminate bias as to which presentation was used first

A gambler wanted to compare two types of poker strategies. One type is playing tight and the other is a loose style of play. It is a common belief that playing tight will win more pots. This belief is tested by having 10 poker players use each type of strategy in a game and comparing the number of pots won under each method of play. A coin flip was used to determine which type of poker strategy each player would follow first. Results indicated that there was no difference in the two types of strategy. Why is a coin used to decide the poker strategy each player would follow first​?

To eliminate bias as to which strategy was used first

Generally, the goal of an experiment is to determine the effect that the treatment will have on the response variable. T/F

True

Randomization is used so that those factors not controlled in the experiment​ "average out" their effect on the response variable. T/F

True