final stats. lest do this. quizes

Why do we sample?

A census is too expensive. A census is time consuming. A census may be impractical. All of the above.

A shoe manufacturer wanted to determine which type of material, "Material X" or "Material Y", to use on the soles of their shoes to get maximum wear. Twenty teenage boys wore one shoe with each type of sole. For each young man, a coin was tossed; if heads, "Material X" would go on the right shoe and "Material Y" on the left. If tails, "Material X" would go on the left shoe and "Material Y" on the right. After wearing these shoes for four months, the thickness of the sole of each shoe was measured. What type of study is this?

A randomized controlled experiment. A simple random sample. A voluntary response sample. A matched pairs experiment.

The college of humanities in a large university was accused of discrimination in their faculty hiring. Twenty records of the recent female applicants who were not hired and twenty records of recent male applicants who were not hired were randomly selected and compared with the records of the recent hires. What type of sampling design is this?

A simple random sample. A stratified sample. A convenience sample A multistage sample.

A computer manufacturer has just received a shipment of 8000 computer chips. In order to ensure that the shipment meets their quality standards, they want to sample a few chips and make a detailed examination of the sample. The chips are packaged individually and have serial numbers. If they use a statistical software package to randomly select serial numbers for 20 chips for inspection, what type of sampling is this?

A simple random sample. A stratified sample. A convenience sample. A multistage sample.

51/1 A television station is interested in predicting whether or not voters are in favor of an increase in the state sales tax. It asks its viewers to phone in and indicate whether they support or are opposed to the proposed increase in order to generate additional revenue for education. What type of sampling design is this?

A simple random sample. A stratified sample. A multistage sample. A voluntary response sample.

A study of religious practices among college students interviewed a sample of 127 students; 107 of the students said that they prayed at least once in a while. Which of the following best describes the sample?

All college students. The college students who believe in a higher power. The 107 college students who pray at least once in a while. The 127 college students who were interviewed.

R.A. Fisher, a famous statistician, describes a well-known design in his book, Design of Experiments. Five varieties of wheat were compared to determine which gave the highest yield in bushels per acre. Eight farms were available for planting. Each farm was divided into five plots. For each farm, the five varieties were randomly assigned to the five plots with one variety per plot. The varieties were planted on their assigned plots and their yields were measured and compared. What type of study is this? How was randomization incorporated into this study?

All five varieties were randomly assigned to the five plots at each farm. The five varieties were randomly assigned to the eight farms - three varieties were planted twice and two varieties only once. It was not incorporated. The wheat seeds were not randomly selected from the population of wheat seeds.

Because more questions about statistics have been added to the state exam, a school district decided to add a probability-statistics unit to their ninth-grade general mathematics course. To determine whether the unit will have an impact on scores on the state exam, all ninth-grade students enrolled in a general mathematics course in the largest high school in the school district were randomly allocated to two groups. One group of 281 students received instruction in a new probability and statistics unit in addition to the traditional instruction; the other group of 311 students received only traditional instruction. Students in both groups were given the state exam at the end of ninth grade to determine whether the group receiving additional instruction in probability and statistics had a higher average score than the group receiving just traditional instruction. What is the population in this study?

All students in ninth grade in the state. The scores of all the students in the state. All students in the traditional unit. All students in the new probability-statistics unit. All students in the ninth-grade general mathematics course in school district.

Which of the following is not part of the Big Picture of Statistics?

Collecting data. Summarizing data. Interpreting data. Publishing research results.

60/1 Is the right hand generally stronger than the left in right-handed people? You can crudely measure hand strength by placing a bathroom scale on a shelf with the end protruding, then squeezing the scale between the thumb below and the four fingers above it. The reading of the scale shows the force exerted. Which of the following best describes the design of a matched pairs experiment to compare the strength of the right and left hands using 10 right-handed people as subjects?

Each subject squeezes the scale twice: once with his right hand and once with his left hand with the order randomly determined. Scale readings are then compared. Each of the ten right-handed people squeeze the scale. Their scale readings are compared with the scale readings of each of the ten left-handed people. Five of the right-handed people squeeze the scale with their right hand, and the other five with their left hand. Scale readings are then compared. Each subject squeezes the scale first with his right hand and then second with his left hand. Scale readings are then compared.

What is the final step in the Big Picture of statistics, as outlined in class?

Exploratory data analysis Inference Produce data Probability

Which of the following is a categorical variable?

Height Phone Number Mile time Book costs

An educational software company wants to compare the effectiveness of its computer animation for teaching about supply and demand curves with that of a textbook presentation. The company tests the economic knowledge of a number of first-year college students, then randomly divides them into two groups. One group uses the animation, and the other studies the text. The company retests all the students and compares the increase in economic understanding in the groups. Is the study described above an experiment? Why or why not?

It is not an experiment because there is no attempt to influence the responses on the tests on economic understanding. It is not an experiment because it does deliberately impose a condition on the first-year college students. It is an experiment because it only measures students' economic knowledge. It is an experiment because the students were randomly assigned to either the animation group or the textbook group.

What does the statistical term "population" refer to?

It refers to a subset of the group we want to study. It refers to a set of principles that guide the study of statistics. It always refers to the United States population. It refers to the group we want to study or learn something about.

Why might collecting data from a sample be preferred over collecting data from a population?

Less expensive. Less time consuming. Collecting data from the entire population may be impossible. All of the above.

High school students are selected by choosing at random several of the city's high schools and then randomly selecting some of the students from those selected high schools. What sampling technique is being used?

Multistage sampling. simple random sampling. stratified sampling. convenience sampling.

Because of concerns about employee obesity and related health problems, a very large company conducted a study to compare two weight-reducing programs (low-carb diet and low-fat diet). Forty employees volunteered to participate in the study for a 10-week period. Half of the employees were randomly assigned to the low-carb diet and the other half randomly assigned to the low-fat diet. What type of study is this?

Observational Study Randomized Controlled Experiment Randomized Block Experiment Matched Pairs Experiment

To investigate the effects of the drug phen-fen, 200 women in the 30-40 age range who had used the drug for at least one year were located. 200 women of the same age group who had not used the drug were also located. The incidence of heart valve abnormality was compared between the two groups. What type of study is this?

Observational Study Randomized Controlled Experiment Randomized Block Experiment Matched Pairs Experiment

A study of computer-assisted learning examined the learning of "Blissymbols" by children. Blissymbols are pictographs (think of Egyptian hieroglyphs) that are sometimes used to help learning-impaired children communicate. The researcher designed two computer lessons that taught the same content using the same examples. One lesson required the children to interact with the material, while in the other the children controlled only the pace of the lesson. Call these two styles "Active" and "Passive", respectively. Children were assigned at random to Active and Passive groups. After the lesson, the computer presented a quiz that asked the children to identify 56 Blissymbols. What type of study is this?

Observational study Experiment

On August 27, 1995, an article in the Los Angeles Times reported that in its survey of 3297 California adults, 2780 (83.4%) had health insurance coverage. These results have a margin of error of ±± 1.4%. What type of study is being described?

Observational study Experiment Neither an observational study nor an experiment

The following situation applies to Questions 3-5: R.A. Fisher, a famous statistician, describes a well-known design in his book, Design of Experiments. Five varieties of wheat were compared to determine which gave the highest yield in bushels per acre. Eight farms were available for planting. Each farm was divided into five plots. For each farm, the five varieties were randomly assigned to the five plots with one variety per plot. The varieties were planted on their assigned plots and their yields were measured and compared. What type of study is this?

Observational study - multistage sample Experiment - randomized block design Experiment - randomized controlled experiment Observational study - simple random sample Observational study - stratified sample

Consider the following two survey questions: Question 1: How satisfied are you with your current job: very satisfied, somewhat satisfied, somewhat dissatisfied, very dissatisfied? Question 2: What do you think can be improved about your job? Are these examples of open or closed questions?

Question 1 is an open question and Question 2 is a closed question Question 1 is a closed question and Question 2 is an open question Both are open questions Both are closed questions

Referring to the question above, was replication incorporated?

Yes, because each treatment group had 20 subjects Yes, because the experiment was repeated on another set of boys No, because the experiment was not repeated on another set of boys Yes, because there was more than one subject in the experiment

What is the major difference between an observational study and an experiment?

Subjects choose their treatment in an experiment. Researchers assign treatments to subjects in an experiment. Experiments frequently have confounding between two variables in their effect on the response variable.

Two hundred twenty-eight children in a study were assigned to one of three groups. Group one was required to consume 5 mg of caffeine or less each day, Group two was required to consume 5-20 mg of caffeine a day, and Group three was required to consume more than 20 mg of caffeine per day. At the end of three weeks, their parents reported the average amount of sleep their child got each night. What is the explanatory variable?

The average amount of sleep a child got each night. Getting more than 20 mg of caffeine per day. The amount of caffeine a child got each night. Those who were in group three.

What is the individual in this study?

The classroom receiving the traditional instruction. The classroom receiving the new instruction. A ninth-grade student enrolled in a general mathematics course. All high school students.

What is the explanatory variable in this study?

The exam taken at the end of the year. The high school a student attended. The type of general mathematics instruction received: new instruction or traditional instruction. The new instruction.

Medical experiments are often double blind in nature. What does this mean?

The subjects in the control group receive a placebo treatment. Neither the subject nor the person evaluating the subject (the doctor or nurse) knows which treatment the subject receives. All data on individuals are kept confidential Subjects are randomly assigned to treatments without the doctor's knowing how the randomizing was done.

To test the effectiveness of using a dab of honey to prevent infection in a cut, parents of children in a childcare facility were instructed to wash the wounds of their children with soap and water and then place a dab of honey on the cut. Each cut was then monitored for infection. At the end of the study, the percentage of cuts that became infected was computed. Why is this NOT a valid experiment?

There is no randomization. There is no blinding - parents may use more care and those monitoring for infection may be less stringent in their diagnosis. There is no control group that gets a placebo for comparison. Parents may be more careful of the cuts of their children since they know they are in an experiment. All of these answers are correct.

What is the purpose of statistics?

To mislead others. To find the right answer. To convert data into useful information. All of the above.

70/1 Referring to the previous question, the variable test scores is quantitative.

True False

True or False: All statistical summaries and conclusions should be reported in context.

True False

True or False: Cause and effect relationships cannot be established from observational studies because the explanatory variable is usually confounded with lurking variables.

True False

True or False: We can establish causation whenever a valid sample (simple random sample, stratified sample, multistage sample, etc.) is taken.

True False

True or False: Without random selection, we cannot appropriately apply the laws of probability to perform inference.

True False

An experiment that doesn't incorporate double blinding is NOT a valid experiment. True False

True False

True or False: Convenience sampling is a type of probability sampling design. True False

True False

When we use a randomized block design we want the subjects within each "block" to be similar but they should be different from block to block. True False

True False

True or False: When sampling from the population of interest, it is a good idea to choose a sample that will represent the population well.

True The sample will only apply to the population that it represents. For example, if we took a sample of students in just section 23 of stat 121, then our results would only represent that section and not the whole class. However, if we took a random sample that included students from all of the sections, this would represent the whole class. False

In a random digit telephone survey, neither people who are homeless nor people who only own a cell phone have land-line telephones that can be called with random digit dialing. What type of bias is this?

Undercoverage bias Non-response bias Response bias due to respondent lying or deliberately giving incorrect information Response bias due to question wording Response bias due to interviewer influences

What type of bias results when people respond differently to questions asked by male interviewers than they do to questions asked by female interviewers?

Undercoverage bias Nonresponse bias Response bias due to respondent lying or deliberately giving incorrect information Response bias due to question wording Response bias due to interviewer effect

A large university in the western United States wants to survey the faculty regarding its plan to combine the spring and summer terms into one semester. It randomly selects 5 colleges on its campus and from each of these colleges, randomly selects 4 departments. Within the chosen departments, 4 faculty members are selected to be included in the sample. What type of sampling design is this? A simple random sample. A stratified sample. A multistage sample. This is a multistage sample because we are taking samples in multiple levels. Level one is when we sample 5 colleges and level 2 is when we sample 4 departments within each college that we samles. So it's a sample within a sample. A convenience sample.

What type of sampling design is this? A simple random sample. A stratified sample. A multistage sample. . A convenience sample.

When are two variables said to be confounded?

When both have the same effect on the response variable. When their effects on the response variable cannot be distinguished from each other. When both variables are explanatory variables. When both variables are treatment variables.

Was using the eight farms as blocks appropriate?

Yes, because each farm was large. Yes, because it removes lurking variables from farm to farm. No, because each fertilizer should be a block.

The following situation applies to Questions 1-5: Because more questions about statistics have been added to the state exam, a school district decided to add a probability-statistics unit to their ninth-grade general mathematics course. To determine whether the unit will have an impact on scores on the state exam, all ninth-grade students enrolled in a general mathematics course in the largest high school in the school district were randomly allocated into two groups. One group of 281 students received instruction in a new probability and statistics unit in addition to the traditional instruction; the other group of 311 students received only traditional instruction. Students in both groups were given the state exam at the end of ninth grade to determine whether the group receiving additional instruction in probability and statistics had a higher average score than the group receiving just traditional instruction. Does this study incorporate the principle of control or comparison?

Yes, because the group of students receiving only traditional instruction can be considered a control or comparison group. The group of students receiving the additional instruction of probability-statistics can be considered the active treatment group. No, because there was not a group of students who did not receive any instruction.

Does the study described incorporate the principle of replication?

Yes, because there were 281 students in one group and 311 in the other group (more than one individual per treatment group) No, because the study was not repeated another year (the experiment only happened once) 31/1

Does the study described incorporate the principle of randomization?

Yes, because we are told that "students . . . were randomly allocated . . ." No, because students registered for whichever section they wanted.

In studies of worker productivity, it has been noticed that any change in the work environment together with the knowledge that a study is underway will produce a short-term increase in productivity. This is known as

placebo effect. Hawthorne effect. diagnostic bias non-compliance.

The group we want to study or learn something about is known as the

sample. population. individual. group.

True or False: The placebo effect happens when subjects improve because they have confidence in the medical provider and hope in the medication, even when they may not be receiving the treatment. True False

true flase