Statistics 3.0

Two researchers randomly select different samples of 20 students from the same population and their sample averages are slightly different. What is this natural difference between random samples called?

Sampling variability

A researcher takes two different random samples from the same population and gets slightly different results. Does this necessarily mean the researcher made a mistake?

No, differences between random samples are natural sampling variability

A researcher increases the size of a random sample. What generally happens to sampling variability?

Sampling variability generally decreases

A researcher uses a very large sample in a phone survey, but people without phones cannot participate. Does the large sample automatically make the study representative?

No, a large sample does not guarantee representativeness

A researcher surveys thousands of people but uses a method that excludes certain members of the population. What should the researcher remember about sample size?

Large sample size does not automatically eliminate sampling bias or guarantee representativeness

A manufacturer produces 16-ounce cans, but the filling machine causes some cans to contain slightly more or less than 16 ounces. What type of variation can occur?

Variation

A researcher calculates several values during a statistical calculation. According to the lecture, when should the researcher round the numbers?

Round only at the end

A frequency table shows that a particular value has a frequency of 3. What does the frequency of 3 mean?

The value occurs 3 times

A class has 20 students and 3 students report studying 2 hours per night. How do you find the relative frequency?

Divide the frequency by the total sample size, so 3 ÷ 20 = 0.15

A class has 20 students and 5 students report studying 3 hours per night. What is the relative frequency?

5 ÷ 20 = 0.25

A frequency table has a relative frequency of 0.15 in the first row and 0.25 in the second row. What is the cumulative relative frequency at the second row?

0.40

A frequency table has relative frequencies of 0.15, 0.25, and 0.15 for the first three rows. What is the cumulative relative frequency at the third row?

0.55

The cumulative relative frequency at a particular value is 0.72. What percentage of observations are at or below that value?

72%

The cumulative relative frequency at a particular value is 0.72. What percentage of observations are above that value?

28%

A researcher wants to study the relationship between two variables by changing one variable and measuring the effect on another. What type of study is this?

Experiment

A researcher changes the amount of medication given to participants. What is the variable being changed called?

Explanatory variable or independent variable

A researcher changes medication dosage and measures participants' blood pressure. What is blood pressure called?

Response variable

A researcher gives participants a placebo, a low dose, or a high dose of a medication. What are the different values assigned to participants called?

Treatments

A researcher gives a treatment to each person participating in a study. What is each person receiving the treatment called?

Experimental unit

A researcher randomly assigns volunteers to different treatment groups. What is the purpose of random assignment?

To help make the treatment groups comparable

A researcher randomly assigns participants to treatment groups so that factors such as age, sex, and other characteristics are spread among the groups. Why is this useful?

It helps balance lurking or confounding variables between treatment groups

A researcher wants to determine whether a treatment itself caused a change in the response variable. Why should the treatment groups be alike in important ways other than the treatment?

To isolate the effect of the explanatory variable

Researchers ask people whether they already take vitamin E and then compare the health of vitamin E users and nonusers. Why is this not a true experiment?

The researchers did not manipulate or assign vitamin E use

Vitamin E users in an observational study also exercise more and eat healthier than nonusers. What are these additional factors called?

Lurking or confounding variables

A study finds that people who regularly take vitamin E have better health, but the researchers did not assign vitamin E use. Can the study prove that vitamin E caused the better health?

No, an observational relationship cannot establish cause and effect

A participant receives an inactive pill but feels better because they believe they received the actual medication. What is this called?

Placebo effect

A clinical trial gives one group a placebo and another group the actual medication. Why is the placebo group used?

To provide a comparison and help account for the placebo effect

Participants in a clinical trial do not know whether they received the actual medication or placebo. What is this called?

Blinding

Participants and the researchers interacting with them do not know which treatment each participant received. What is this called?

Double blinding

Researchers test two masks in a maze. Participants know which mask they received because one has a noticeable scent, but the researchers recording completion times do not know. Who is blinded?

The researchers recording the results are blinded

Researchers cannot blind participants because they can tell which treatment they received. Can researchers still use blinding?

Yes, the researchers measuring or recording the outcomes can be blinded

A researcher observes that two variables are related. Does this automatically prove that one variable caused the other?

No, correlation does not prove causation

Researchers randomly assign participants to treatment groups and find that one treatment produces a different outcome. What type of conclusion can random assignment help support?

A cause-and-effect conclusion

A researcher randomly selects people from a population before a study. What is the purpose of random sampling?

To help obtain a representative sample

A researcher randomly assigns selected participants to different treatment groups. What is the purpose of random assignment?

To help create comparable treatment groups and support cause-and-effect conclusions

A researcher uses random sampling and random assignment in the same study. Are these two processes the same?

No, random sampling concerns selecting people from the population, while random assignment concerns assigning selected participants to treatments

A statistician is involved in a clinical trial before the study begins. What important task can the statistician help determine?

The sample size needed for the study

Researchers conduct a study involving human participants. Which federal department oversees regulations concerning human research?

U.S. Department of Health and Human Services

A research study involving human participants must be reviewed and monitored before and during the study. What organization performs this role?

Institutional Review Board or IRB

An IRB determines that participants are being harmed during a study. What can the IRB do?

The IRB can stop the study

A research study gives participants information about the study and its risks before they agree to participate. What ethical requirement is this?

Informed consent

A clinical trial collects participants' personal information and protects it from being improperly disclosed. What ethical principle is involved?

Participant privacy

A researcher is designing a human study and must minimize possible harm to participants. What ethical principle from the lecture applies?

Risks should be minimized

A clinical trial is approved before participants are enrolled. Why is advance approval important?

It helps protect human participants and ensure the study meets ethical requirements