Question 1

To reduce bias in experimental results, all of these are useful except for which one?

Accepted Answer

Alternating procedure for assigning participants does not reduce bias effectively as it can introduce systematic differences between treatment groups, unlike random assignment which ensures each participant has an equal chance of being assigned to any group, thus minimizing bias.

Question 2

Which of these is not a good method to reduce sampling error in experimental results?

Accepted Answer

B

Question 3

An experimental unit is an individual or a group of individuals who have been assigned to an experimental treatment ___________ other individuals or groups.

Accepted Answer

An experimental unit is assigned to an experimental treatment independently of other individuals or groups to ensure unbiased results.

Question 4

What is a control group?

Accepted Answer

A control group in an experiment is a set of subjects that do not receive the treatment being tested, allowing researchers to compare outcomes between those who received the treatment (the experimental group) and those who did not (the control group). This helps in isolating the effects of the treatment.

Question 5

When testing a new drug for an illness, which of these is a major reason to use a control group?

Accepted Answer

Control groups help to account for the placebo effect, where individuals may show improvement simply because they believe they are receiving treatment, not necessarily because the treatment itself is effective.

Question 6

When testing a new drug for an illness, which of these is not a major reason to use a control group?

Accepted Answer

Using a control group primarily helps in distinguishing the effects of the drug from other factors such as the placebo effect, the natural progression of the illness, and the stress of treatment. It does not serve to distinguish the effects of different drugs from one another; that would require a different experimental setup, often involving multiple control groups or a comparative study design.

Question 7

If the experiment involves giving drugs, we provide a ____ to the control group, whereas if the experiment involves surgical procedures, we provide a ____ operation to the control group.

Accepted Answer

In experiments involving drugs, a "placebo" is given to the control group to mimic the treatment without therapeutic effect. For surgical procedures, a "sham" operation is performed on the control group to mimic the surgery without actually performing it.

Question 8

In experiments, when only the study subjects don't know which treatment group they are in, we call this a ____ - blind study, whereas if both the subjects and the people administering the treatment don't know, we call this a ____ - blind study.

Accepted Answer

A single-blind study is when only the participants are unaware of which group they belong to, while a double-blind study is when both the participants and the researchers do not know who has been assigned to which group.

Question 9

Why is blinding important when designing studies?

Accepted Answer

Blinding is important to prevent researchers from unintentionally treating participants differently based on their knowledge of who is receiving the treatment or placebo, which could bias the results.

Question 10

Increasing the sample size reduces the magnitude, or risk, of all of the following except which one?

Accepted Answer

Increasing the sample size does not reduce bias, which is a systematic error in the measurement process. Bias is related to the methodology of a study and not the sample size.

Question 11

True replication is more than just the absolute number of experimental units; the units considered must be ______ as well.

Accepted Answer

True replication requires that the experimental units be independent to ensure that the results from one unit do not influence the results from another. This independence is crucial for the validity of statistical analyses.

Question 12

If the DNA sequences of a bunch of individuals from a family with a history of a specific genetic disease are compared to DNA sequences in a data base, what limits the power of tests to discover the causes of the disease?

Accepted Answer

Family members share a significant portion of their genetic material, which reduces the effective sample size and limits the power of tests to identify disease-causing variants.

Question 13

When treatments in a study have different sample sizes, we say it is which of the following?

Accepted Answer

When treatments in a study have different sample sizes, it is referred to as "unbalanced." This term is used in the context of experimental design and statistical analysis to indicate that the number of observations or subjects is not the same across all groups or treatment levels.

Question 14

Experiments with two treatments per block are _____ designs, and experiments with more than two treatments per block are _____ designs.

Accepted Answer

Experiments with two treatments per block are known as paired designs because each block can be thought of as containing a pair of experimental units. When there are more than two treatments per block, the design is referred to as a randomized block design, which allows for the control of block effects while randomizing treatments within blocks.

Question 15

Why is it important to be cautious when judging the results of an experiment comparing extremely different treatments to one another?

Accepted Answer

The answer of Why is it important to be cautious...

Question 16

Consider the figure shown indicating the results on an experiment growing a marine invertebrate in four different environments based on values of two factors. Two different temperatures and two different salinities were used. Which of the following is correct?
​
 ​

Accepted Answer

The answer of Consider the figure shown indicating the results...

Question 17

Consider the figure shown indicating the results on an experiment growing a marine invertebrate in four different environments based on values of two factors. Two different temperatures and two different salinities were used. Which of the following is incorrect?
​
 ​

Accepted Answer

The answer of Consider the figure shown indicating the results...

Question 18

Which of the following aspects of good experimental design is the one that observational studies are unable to provide?

Accepted Answer

Randomization is a key aspect of experimental design that observational studies cannot provide. Randomization helps to ensure that any differences observed between groups in an experiment can be attributed to the treatment effect rather than to preexisting differences between the groups. Observational studies, by contrast, do not involve the researcher controlling the assignment of treatments, so they cannot ensure this balance through randomization.

Question 19

What are the primary benefits of matching when doing observational studies?

Accepted Answer

Matching in observational studies primarily aims to reduce bias and sampling error by ensuring that the groups being compared are as similar as possible on certain characteristics, thereby controlling for those variables.

Question 20

Consider estimating the 95% confidence interval for the difference between two population means with a desired margin of error of 5 cm. What would the approximate (i.e., using the 2SE rule of thumb) minimum sample size be for each of the samples if the population standard deviation is 15 cm?

Accepted Answer

The formula for the margin of error (ME) in estimating the difference between two means is ME = z * sqrt((σ₁²/n₁) + (σ₂²/n₂)), where z is the z-score for the desired confidence level, σ₁ and σ₂ are the population standard deviations, and n₁ and n₂ are the sample sizes. For a 95% confidence interval, z is approximately 1.96. Assuming equal standard deviations (σ₁ = σ₂ = 15 cm) and equal sample sizes (n₁ = n₂ = n), the formula simplifies to ME = 1.96 * sqrt(2 * 15² / n). Setting ME to 5 cm and solving for n gives n ≈ 72.

Quiz 14: Designing Experiments

To reduce bias in experimental results, all of these are useful except for which one?

Which of these is not a good method to reduce sampling error in experimental results?

An experimental unit is an individual or a group of individuals who have been assigned to an experimental treatment ___________ other individuals or groups.

What is a control group?

When testing a new drug for an illness, which of these is a major reason to use a control group?

When testing a new drug for an illness, which of these is not a major reason to use a control group?

If the experiment involves giving drugs, we provide a to the control group, whereas if the experiment involves surgical procedures, we provide a operation to the control group.

In experiments, when only the study subjects don't know which treatment group they are in, we call this a - blind study, whereas if both the subjects and the people administering the treatment don't know, we call this a - blind study.

Why is blinding important when designing studies?

Increasing the sample size reduces the magnitude, or risk, of all of the following except which one?

True replication is more than just the absolute number of experimental units; the units considered must be ______ as well.

If the DNA sequences of a bunch of individuals from a family with a history of a specific genetic disease are compared to DNA sequences in a data base, what limits the power of tests to discover the causes of the disease?

When treatments in a study have different sample sizes, we say it is which of the following?

Experiments with two treatments per block are _ designs, and experiments with more than two treatments per block are _ designs.

Why is it important to be cautious when judging the results of an experiment comparing extremely different treatments to one another?

Consider the figure shown indicating the results on an experiment growing a marine invertebrate in four different environments based on values of two factors. Two different temperatures and two different salinities were used. Which of the following is correct?

Consider the figure shown indicating the results on an experiment growing a marine invertebrate in four different environments based on values of two factors. Two different temperatures and two different salinities were used. Which of the following is incorrect?

Which of the following aspects of good experimental design is the one that observational studies are unable to provide?

What are the primary benefits of matching when doing observational studies?

Consider estimating the 95% confidence interval for the difference between two population means with a desired margin of error of 5 cm. What would the approximate (i.e., using the 2SE rule of thumb) minimum sample size be for each of the samples if the population standard deviation is 15 cm?

Quiz 14: Designing Experiments

To reduce bias in experimental results, all of these are useful except for which one?

Which of these is not a good method to reduce sampling error in experimental results?

An experimental unit is an individual or a group of individuals who have been assigned to an experimental treatment ___________ other individuals or groups.

What is a control group?

When testing a new drug for an illness, which of these is a major reason to use a control group?

When testing a new drug for an illness, which of these is not a major reason to use a control group?

If the experiment involves giving drugs, we provide a ____ to the control group, whereas if the experiment involves surgical procedures, we provide a ____ operation to the control group.

In experiments, when only the study subjects don't know which treatment group they are in, we call this a ____ - blind study, whereas if both the subjects and the people administering the treatment don't know, we call this a ____ - blind study.

Why is blinding important when designing studies?

Increasing the sample size reduces the magnitude, or risk, of all of the following except which one?

True replication is more than just the absolute number of experimental units; the units considered must be ______ as well.

If the DNA sequences of a bunch of individuals from a family with a history of a specific genetic disease are compared to DNA sequences in a data base, what limits the power of tests to discover the causes of the disease?

When treatments in a study have different sample sizes, we say it is which of the following?

Experiments with two treatments per block are _____ designs, and experiments with more than two treatments per block are _____ designs.

Why is it important to be cautious when judging the results of an experiment comparing extremely different treatments to one another?

Consider the figure shown indicating the results on an experiment growing a marine invertebrate in four different environments based on values of two factors. Two different temperatures and two different salinities were used. Which of the following is correct? ​ ​

Consider the figure shown indicating the results on an experiment growing a marine invertebrate in four different environments based on values of two factors. Two different temperatures and two different salinities were used. Which of the following is incorrect? ​ ​

Which of the following aspects of good experimental design is the one that observational studies are unable to provide?

What are the primary benefits of matching when doing observational studies?

Consider estimating the 95% confidence interval for the difference between two population means with a desired margin of error of 5 cm. What would the approximate (i.e., using the 2SE rule of thumb) minimum sample size be for each of the samples if the population standard deviation is 15 cm?

If the experiment involves giving drugs, we provide a to the control group, whereas if the experiment involves surgical procedures, we provide a operation to the control group.

In experiments, when only the study subjects don't know which treatment group they are in, we call this a - blind study, whereas if both the subjects and the people administering the treatment don't know, we call this a - blind study.

Experiments with two treatments per block are _ designs, and experiments with more than two treatments per block are _ designs.

Consider the figure shown indicating the results on an experiment growing a marine invertebrate in four different environments based on values of two factors. Two different temperatures and two different salinities were used. Which of the following is correct?

Consider the figure shown indicating the results on an experiment growing a marine invertebrate in four different environments based on values of two factors. Two different temperatures and two different salinities were used. Which of the following is incorrect?