What is the purpose of a control group in an experiment?

A control group is used to provide a baseline for comparing the effects of other treatments

A control group is used to create groups that are roughly equivalent at the beginning of the experiment.

A control group is used so the subjects don’t know which treatment group they are in.

A control group is used because some subjects in an experiment will respond favorably to any treatment, even an inactive treatment.

Random assignment in an experiment is used to ______.

ensure each participant has an equal chance of being assigned to any group

increase the number of participants

reduce the time of the experiment

It is estimated that ten percent of the population is left-handed. Mrs. Ngo, the statistics teacher, thought that her school had more left-handed people, so she selected a random sample of 30 students from the school and found that 7 students were left-handed. She also ran a simulation 40 times to simulate the number of students out of 30 that would be left-handed if the actual proportion in the population were 10%. Based on the dotplot, does Mrs. Ngo’s sample provide convincing evidence that the proportion of students at her school is greater than 10%?

Yes, because only one of the simulations had 7 or more students that are left-handed.

Yes, because the simulation is not symmetric with a center of 3 left-handed students.

No, because one out of the 40 simulations had more than 7 left-handed students.

Yes, because none of the simulations had exactly 7 students that are left-handed.

In order to estimate the proportion of students that are in favor of starting school two weeks earlier, the school emailed all of the students and asked them their opinion. Of the 42% of the students that responded, 21% were in favor of starting school two weeks earlier. What potential bias is present in the design of this survey and is the sample proportion likely to be an overestimate or underestimate of the population proportion?

The sample proportion is likely to be an overestimate because of nonresponse bias.

The sample proportion is likely close to the true proportion because the sample is an SRS of apartments in the building.

The sample proportion is likely to be an overestimate because of response bias.

The sample proportion is likely to be an overestimate because of undercoverage bias.

A random sample of size 25 was selected from a list of all of the mystery novels written in the last 2 years to estimate the average number of pages per book for new mystery novels. This process was repeated for a total of 100 different sample averages for samples of size 25. Which of the following would reduce the sampling variability of the average number of pages per book in different random samples of different sizes from all of the students at the school?

Increase the sample size from 25 to 80 and keep the number of samples at 100.

Decrease the sample size from 25 to 10 and keep the number of samples at 100.

Keep the sample size the same but increase the number of samples to 200 instead of 100.

Keep the sample size the same but decrease the number of samples to 100 instead of 50.

The most important advantage of experiments over observational studies is that

experiments can give better evidence of causation.

experiments are easier to carry out.

an observational study cannot be generalized to a larger population of interest.

an observational study cannot have a response variable.

experiments can provide results that are statistically significant, while observational studies cannot.

Two studies are described below. Determine if each study is an experiment or an observational study. Study 1: A farmer believes that applying a growth hormone to the soil will produce larger tomatoes. The farmer prepares his land exactly the same, but on half of the land, he also adds the growth hormone to the soil. When the tomatoes were ready to pick, the land with the growth hormone produced, on average, significantly larger tomatoes. Study 2: A teacher believes that using group activities for students helps students to remember the material better than traditional lecturing. To help determine if this is true, she teaches two classes with traditional lecturing and two different classes using group activities. The students in the classes that learned using group activities earned significantly higher scores than the students in classes that were taught using traditional lecture.

Both of the studies described are experiments.

The first study described is an experiment and the second one is an observational study.

The first study described is an observational study and the second one is an experiment.

Neither of the studies described are experiments.

A new scanning process at the airport was developed to decrease the time it takes to go through screening. A study was conducted to see if this new process worked better than the current process. A random sample of 10 airports was selected, and at each airport four screening checkpoints were randomly selected. Two of the screening checkpoints were randomly chosen to use the new screening process and the other two used the current screening process. The results showed that the time required to get through screening using the new process was, on average, less than the time using the current process and the time difference was statistically significant. Based on the design of the study, which of the following is true?

The results can be generalized to all airports and we can conclude that the new process causes a decrease in time required to get through screening.

The results cannot be generalized to all airports and we cannot conclude that the new process causes a decrease in time required to get through screening.

The results can be generalized to all airports, but we cannot conclude that the new process causes a decrease in time required to get through screening.

The results cannot be generalized to all airports, but we can conclude that the new process causes a decrease in time required to get through screening

No conclusion can be made because the sample size is too small.

When flipping a fair coin, the coin should land heads up 50% of the time A magic store sells a coin that they claim is not fair. In other words, the proportion of heads when the coin is flipped is actually greater than 0.50. To test this claim, Regina flipped the coin the store sells 40 times and noted that 30 times the coin was heads up. She also ran 200 simulations of size 40 assuming the coin is fair and the results are shown below. Based on the dotplot, does Regina’s original sample of 40 flips provide convincing evidence that the proportion of heads is greater than 50%?

Yes, because only 0.5% of the simulations had a sample count of at least 30 heads.

No, because one of the simulations resulted in a sample with 31 heads which is larger than 30.

No, because the simulation is symmetric with a center of 20 heads.

Yes, because none of the simulations resulted in a sample with 30 heads.

An experiment was conducted to see if a new mosquito repellant worked better than the current brand. Twenty volunteers were randomly assigned to one of two groups. The first group used the new repellant and the second group used the old repellent. Each participant placed their arms in a bin containing mosquitos and the number of bites on their arm was counted after ten minutes. The group that used the old repellant had, on average, 4 more bites on their arms than the group that used the new repellant. Using the data from the experiment, 200 trials of a simulation were performed and the dotplot below shows the average differences in each trial. Based on the dotplot, are the results statistically significant?

Because the difference of 4 only occurred once out of 200 trials, the results are statistically significant. The new repellant seems to work better than the old repellant.

Because there was a trial that had a sample mean difference of 4, the results are not statistically significant. The new repellant seems to work better than the old repellant.

Because the simulations have a center of 0, the results are not statistically significant. The new repellant does not seem to work better than the old repellant.

Because the difference of 4 only occurred once out of 200 trials, the results are not statistically significant. The new repellant does not seem to work better than the old repellant.

Because more than 5% of the trials were more than 0, the results are not statistically significant. The new repellant does not seem to work better than the old repellant.

A school health teacher at a high school wants to determine the proportion of students who sleep at least 8 hours each night. An optional survey is offered as bonus, asking if they typically get at least 8 hours of sleep per night. Students who return the survey get 5 bonus points. The health teacher finds that 75% of the completed surveys indicated that the students sleep at least 8 hours each night. Which of the following is true about the sample proportion obtained from this sample?

The sample is biased and overestimates the proportion because of voluntary response sampling.

The sample is not biased and the sample proportion should be approximately the same as the actual proportion.

The sample is biased and overestimates the proportion because of random sampling

The sample is biased and overestimates the proportion because of convenience sampling.

The sample is not biased and 75% of the students at this school sleep at least 8 hours each night.

A local news agency conducted a survey about unem-ployment by randomly dialing phone numbers until it had gathered responses from 1000 adults in the state. In the survey, 19% of those who responded said they were not currently employed. In reality, only 6% of the adults in the state were not currently employed at the time of the survey. Which of the following best explains the difference in the two percentages? ployment by randomly dialing phone numbers until it had gathered responses from 1000 adults in the state. In the survey, 19% of those who responded said they were not currently employed. In reality, only 6% of state were not currently employed the adults in at the time of the survey. Which of the following best explains the difference in the two percentages? (a) The difference is due to sampling variability

The difference is due to nonresponse. Adults who are employed are less likely to be available for the sample than adults who are unemployed. 5. A study of treatments for angina (pai

The difference is due to sampling variability. We shouldn’t expect the results of a random sample to match the truth about the population every time.

The difference is due to response bias. Adults who are employed are likely to lie and say that they are unemployed.

The difference is due to undercoverage. The survey included only adults and did not include teenagers who are eligible to work.

To examine the impact of question wording on survey results, Sam and Joshan randomly selected 60 students from their school’s student list and divided them at random into two groups of 30. By email, they asked the students the following questions about a nearby convenience store, the Quick Shop: Group 1 Question (“Markup”): Do you think the prices at the Quick Shop are fair, given that the typical markup is 25%? Group 2 Question (“Convenience”): Keeping in mind the convenient location of the Quick Shop, do you think the prices are fair, given that the typical markup is 25%? Select the type of research study and the reason.

Treatments were imposed. Some students were given the “Markup” version of the question and others were given the “Convenience” version of the question.

Monitors were imposed. Some students were observed how they respond to the “Markup” version of the question and others were observed how they respond to the “Convenience” version of the question.

What is a completely randomized design?

A design where treatments are assigned randomly to experimental units.

A design where treatments are assigned based on size.

A design where treatments are assigned based on color.

A design where treatments are assigned based on weight.

What does it mean if the results of an experiment are statistically significant?

The results are larger than expected by chance.

The results are due to random chance.

The results are not significant.

What is the primary purpose of an Institutional Review Board (IRB)?

To protect the rights and welfare of human subjects

To decide if a study will produce valuable information

To ensure a study is statistically sound

To approve all research activities.

What is the primary purpose of obtaining informed consent from subjects in a study?

To ensure subjects are aware of the study's nature and risks

To comply with legal requirements

What is the primary reason for maintaining confidentiality in studies?

To protect individuals' privacy

A manager of a cable news station designed a study to see if one yawning person causes another person to yawn. Volunteers were informed they were in an experiment about repeated behavior and were split into two groups. Hidden cameras were set up and the volunteers in each group were individually asked to go into a room with two other people, both of whom were paid actors. The volunteers were told that they were part of a focus group about a new product, but during their 30 minute discussion, the paid actors purposely yawned and the proportion of times the volunteer also yawned was recorded. The paid actors for the volunteers in group A yawned every 5 minutes and the paid actors for the volunteers in group B yawned every 10 minutes. The volunteers did not know they were being recorded. Which of the following is true about this study?

The study is unethical because the participants in the study did provide informed consent, but their information was not kept confidential.

The study is unethical because the participants in the study did not provide informed consent and their information was not kept confidential.

The study is unethical because the participants in the study did not provide informed consent although their information was kept confidential.

The study is ethical because the participants in the study did provide informed consent and their information was kept confidential.

An experiment was designed to see if regular exercise can help lower blood pressure for patients with high blood pressure. A researcher wanted to test this theory, and told a group of volunteers with high blood pressure that exercise may work better than any other treatment for high blood pressure. For the next month, the researcher assigned participants to two groups. One group was enrolled in a physical fitness program and the other group was prescribed a medicine to lower blood pressure. At the end of the month, the blood pressure in the volunteers, on average, decreased approximately the same from the blood pressure at the beginning of the month for both groups of participants. Which of the following is true about this experiment?

The fact that the average decrease was not significantly different for both groups may be due to the placebo effect, so it may not be true that exercise works better than any other treatment.

Because the researcher is the one that picks the group of patients that exercise, the patients are blinded to the treatment and the decrease in blood pressure is caused by the exercise routine or the medicine.

Because the test results were not significantly different, there is reason to believe that exercise works better than any other treatment.

The experiment is well-designed, but the researcher needs to increase the time of the experiment to a whole year.

Summative 6 Term 2

Authored by Armina Wrice

Mathematics

12th Grade

CCSS covered

Used 6+ times

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40 questions

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MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Which of the following is a key consideration when designing experiments to establish causal relationships?

Randomization

Sample Size

Control Group

All of the above.

Tags

CCSS.HSS.IC.B.5

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

In experimental design, minimizing _______ is crucial to establish valid causal relationships.

A) Bias

B) Variability

C) Both A and B

D) None of the above

Tags

CCSS.HSS.IC.B.5

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Use data from a randomized experiment to compare two treatments. Use _______ to decide if differences between parameters are significant.

A) Simulations

B) Surveys

C) Observations

D) Randomization

Tags

CCSS.HSS.IC.B.5

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Which of the following methods can be used to randomly assign treatments in an experiment?

Using slips of paper

Using a computer program

Both A and B

None of the above.

Tags

CCSS.HSS.IC.B.5

CCSS.HSS.IC.B.3

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

The purpose of random assignment in an experiment is to ______.

Increase variability

Reduce bias

Ensure equal sample sizes

None of the above.

Tags

CCSS.HSS.IC.B.3

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Fill in the blank: If treatments are given to groups that differ greatly when the experiment begins, _______ is likely.

success

confounding

accuracy

consistency

Tags

CCSS.HSS.IC.B.5

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

What is one reason why allowing students to choose their group in an experiment about caffeine tolerance might affect the results?

It ensures random assignment

It introduces additional variables

It eliminates bias

It guarantees equal group sizes.

Tags

CCSS.HSS.IC.B.5

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Summative 6 Term 2

Which of the following is a key consideration when designing experiments to establish causal relationships?

In experimental design, minimizing _______ is crucial to establish valid causal relationships.

Use data from a randomized experiment to compare two treatments. Use _______ to decide if differences between parameters are significant.

Which of the following methods can be used to randomly assign treatments in an experiment?

The purpose of random assignment in an experiment is to ______.

Fill in the blank: If treatments are given to groups that differ greatly when the experiment begins, _______ is likely.

What is one reason why allowing students to choose their group in an experiment about caffeine tolerance might affect the results?

In an experiment, _______ means that treatments are assigned to experimental units using a chance process.

What is the purpose of a control group in an experiment?

What is the primary purpose of random assignment in an experiment?

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