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Statistics Chapters 1-6
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The telephone company says that 62% of all residential phone numbers in Los Angeles are unlisted. A telephone survey contacts a random sample of 1,000 Lis Angeles telephone number, of which 58% are unlisted. In this setting.
62% is a parameter and 58% is a statistic.
A recent Gallup Poll asked, "what is your favorite summer Olympics event?" Of the people asked, 27% said swimming." Here is what Gallup says about the accuracy of the poll:
The results are based on telephone..
In Gallup statement, "95% confidence" means (assuming not bias)
If Gallup repeated this poll many times, 95% of the results would be within plus or minus three percentage points of the truth about the population.
Which of the following is correct?
Parameters describes population characteristics.
If we take many simple random samples from the same population we expect.
The values of statistics will vary from sample to sample.
To reduce the variability of estimates from a simple random sample, you should
Use a larger sample.
The margin of error for a poll is 4% this means that
We have 95% confidence that the sample statistic is within 4% of the population parameter.
For what confidence level are margins of error usually reported?
95%
A 2008 national sample survey interviewed 1,007 people age 18 and older nationwide by telephone. One question asked was whether "on the whole would you say you are satisfied or dissatisfied with the way the nation is being governed?
The news article that reports the poll results says, "one can say with 95% confidence that the margin of error is plus or minus three percentage points." this means
We can be 95% confident that between 23% and 29% of all Americans are satisfied with the way the nation is being governed.
If we choose a simple random sample (SRS) from a population, we can be sure that the ____which we compute from our SRS is an ___estimate of the populations true____. We also know that we can reduce the _____ of our result as desired by taking a large enough sample. The appropriate sequence of words to complete this stagment is.
Statistic, unbiased; parameter;variation
A psychologist wants to know if adults with normal vision can be fooled by a certain optical illusion. She recruits 50 students from her PSY 120 class and finds that 42 of them are fooled by the illusion. The population in this study is.
All adults with normal vision
when we take a census, we attempt to collect data from
every individual in the population
in a(n)______, the environment of the subjects controlled or manipulated by the researcher
experiment
You measure the age (years), weight (pounds), and martital status of 1,400 women. How many variables did you measure?
three
A sports writer wants to know how strongly Columbus, Ohio residents support building a new stadium for the local minor league baseball team, the Columbus Clippers. She stands outside of the stadium before a game and interviews the first 25 people who enter the stadium.
The population for this survey is?
All residents of Columbus Ohio
A sports writer wants to know how strongly Columbus, Ohio residents support building a new stadium for the local minor league baseball team, the Columbus Clippers. She stands outside of the stadium before a game and interviews the first 25 people who enter the stadium.
The Sample of this Survey is?
the 25 people who gave the sports writer their opinion
Can pleasant aromas help people work more efficiently? Researchers did this study to find out. Twenty-two students worked a paper-and-pencil maze six times. On three tries, they wore a mask with floral scents. On the other three times they wore a mask with no scent. The six tries were done random order and each used a different maze. The researchers found that the subjects took less time to complete the maze when wearing a scented mask.
This study is
an experiment
a recent survey of 35,101 randomly selected U.S adults studied the religious affiliation of Americans. The sample for this survey is
The 35,101 people questioned.
You want to know the opinions of American school teachers about establishing a national test for high school graduation. You obtain a list of the members of the National Education Association (The largest teacher union) and mail a questionnaire to 2500 teachers chosen at random form this list. In all 1,347 teachers return the questionnaire.
In this situation, The population is
All American School Teachers
You want to know the opinions of American school teachers about establishing a national test for high school graduation. You obtain a list of the members of the National Education Association (The largest teacher union) and mail a questionnaire to 2500 teachers chosen at random form this list. In all 1,347 teachers return the questionnaire.
The Sample is
the 1,347 teachers who mailed back the questionnaire
The student newspaper runs a weekly question that readers can answer online or by campus mail. One question was "Do you think the college is doing enough to provide student parking?" of the 82 people who responded, 79% said "No."
When we say that the news paper poll is biased, we mean that
Repeated polls would miss the truth about the population in the same direction.
Your statistics recitation has 30 students. You want to call an SRS of 5 students from your recitation to ask where they use a computer for the online exercises. You label the students 01,02.........30 you enter the table in random digits at this line.
14459 26056 31424 80371 65103 22490 61181
14 03 10 22 06
A table of random numbers is used to select 30 students from a statistics class to rate a statistics video. These 30 students are
simple random sample of the class
A table of random numbers is used to select 30 students from a statistics class to rate a statistics video. The ratings that these students give are used to estimate the ratings that would be given if the entire class were asked to rate the video. The average of the ratings of all students in the class is
a statistic that is unbiased estimate of the class rating
For a sample to be a simple random sample of size N
Every collection of n individuals must have the same chance to be the sample actually chosen.
You must choose a simple random sample of 8 lots from a shipment of 80 lots of vaccine for testing. You label the lots 01,02,03,....80. and then use the random number table to select your sample. the chance that any one lot is chosen for the sample is
1 in 10
There are 34 students in you statistics section. You want to choose an SRS of 3 of these students. A correct way to assign labels to the 34 students before using the random digit table is
Only (a) and C are correct
voluntary response polls almost always suffer from
High Bias
Bias in sampling method is
any systemic error that tends to occur in the same direction every time you use this sampling method
A sports writer wants to know how strongly Columbus, Ohio residents support building a new stadium for the local minor league baseball team, the Columbus Clippers. She stands outside of the stadium before a game and interviews the first 25 people who enter the stadium.
the newspaper asks you to comment on their survey of local opinion. You say
the sampling method is biased. It will certainly overestimate the level of support among all Columbus, Ohio residents.
The student newspaper runs a weekly question that readers can answer online or by campus mail. One question was "Do you think the college is doing enough to provide student parking?" of the 82 people who responded, 79% said "No."
The newspaper poll does not give a trustworthy estimate of student opinion because of
Bias due to relying on voluntary response.
A census Bureau report on the income of Americans say that with 90% confidence the median income of all California households in 2007 was $67,484 with a margin of error or $375. Suppose that many of the households asked their income by the census Bureau give an answer that is too low because they fear that their answer will go to the Internal Revenue service.
This is a nonsampling error that causes bias.
We divide the class into two groups: First year students and others. We then take a random samples from each group. This is an example of
Stratified random sampling
A 2008 national sample survey interviewed 1,007 people age 18 and older nationwide by telephone. One question asked was whether on the whole would you say you are satisfied of dissatisfied with the way the nation is being governed?
Both a and c
Which of the following is a source of nonsampling error in a sample survey?
none of these
Which of the following is not a source of nonsampling error
Choosing the sample from shoppers at a suburban mall
A sample of student opinion at a Big Ten University selects a SRS of 200 of 30,000 undergraduate students and a separate SRS of 100 of the 5,000 graduate students. This kind of sample is called
Stratified random sample
You want to estimate the proportion of undergraduates at a college who favor eliminating evening exams and you do so by taking a sample of undergraduates. Which of the following are sources of nonsampling errors
a and b but not c
When a sample survey asks people about use of illegal drugs, some people who use drugs will deny that they do because they fear that information will be given to the police or employers
this is a nonsamplings error that causes bias.
One source of error in pre-election polls is that some people in the sample say they will vote but later do not vote. this is an example of
non sampling error
The New York times conducted a poll on women's issues in June of 1989
The poll omitted people without telephones, and also left out Alaska and Hawaii to reduce cost. These omissions may cause a small bias is
a sampling error
A gallup poll recently showed that 69% of Americans believe there is a hell. The poll contacted 1,003 adults by phone. The margin of sampling error was plus or minus three percentage points. Assume a 95% confidence level. The poll has some bias because the sample leaves out people without a phone. This bias
Is not included in the margin of error because the margin of error only covers the chance variation in a random sample.
BLANK A try to gather data without influencing the reponse of BLANK B on the other hand impose some BLANK C in order to observe the response
BLANK A SHOULD READ
Observational studies
BLANK A try to gather data without influencing the reponse of BLANK B on the other hand impose some BLANK C in order to observe the response
blank B should read
a experiment
BLANK A try to gather data without influencing the reponse of BLANK B on the other hand impose some BLANK C in order to observe the response
BLANK C SHOULD READ
treatment
Confounding often defeats attempts to show that one variable causes changes in another variable. Confounding means that
The effects of several variables are mixed up, so we cannot say which is causing the response.
The drug manufacture Merk recently stopped testing a promising new drug to treat depression. It turned out that that in a randomized, double-blind trial a dummy pill did almost as well as the new drug. The fact that many people respond to a dummy treatment is called
The Placebo Effect
Corn Variety #1 yielded 140 Bushels per acre last year at a research farm. This year, corn variety #2 planted in the same location, yielded only 110 bushels per acre. Unfortunately, we don't know whether the difference is due to the superiority of variety of #1 or the effect of this years drought. This is an example of
Confounding
A study at Yale Medical School investigated treatments for chronic cocaine abusers of the 72 subjects all cocaine users who wanted to quit 24 were assigned at random to each other the three drugs, A. Desipramine B. Lithium, C. a placebo. After six weeks the subject reported whether they had stayed off cocaine.
The explanatory variable in the Yale Study is
Which drug a subject was given
A study at Yale Medical School investigated treatments for chronic cocaine abusers of the 72 subjects all cocaine users who wanted to quit 24 were assigned at random to each other the three drugs, A. Desipramine B. Lithium, C. a placebo. After six weeks the subject reported whether they had stayed off cocaine.
The response variable in the Yale study is
Whether or not a subject stayed off cocaine
Men who have worked as coal miners for many years generally have lung problems. They call their problems black lung disease. Suppose however that almost all coal miners smoke. This is an example of
Confounding
A study compares online instruction with a standard lecture for teaching statistics.
The proper way to design such as study is
do a randomized comparative experiment in which half of the students are assigned to online instructions and half to a lecture.
A study compares online instruction with a standard lecture for teaching statistics.
The report of the study says, "With 95%Confidence, we can say that students who used online instruction raise their average statistic scores by between 12 and 18 points more than students who attended lectures." By 95% confidence we mean
We got the 12 to 18 point range by using a method that would give a correct answer in 95% of all samples
You have invented a drug that you think will relieve anxiety and help students score better on exams. You want to test the drug on a group of statistics students who are about to take their final exam.
You will give some students your new drug and others the dummy pill, why?
to avoid confounding with the placebo effect.
You have invented a drug that you think will relieve anxiety and help students score better on exams. You want to test the drug on a group of statistics students who are about to take their final exam.
how will you decide which students gets your drug?
choose an SRS of half of the available students
You have invented a drug that you think will relieve anxiety and help students score better on exams. You want to test the drug on a group of statistics students who are about to take their final exam.
What is a reasonable response variable for the experiment?
A students score on a statistics final exam
The most important advantage of experiments over observational studies is that
experiments can give better evidence of causation
Is St. John's wort effective in treating attention-deficit/hyperactivity disorder (ADHD) in children and adolescents? A report in a recent issue of the Journal of American Medical Association describes a study to answer this question
A randomized, double-blind, placebo-controlled trial was conducted involving 54 children aged 6 to 17 years. Participants were randomly assigned to receive 300 MG of St.Johns wort (27 Subjects) or matched placebo (27 subjects) 3 times daily for 8 weeks.
Results ADHD rating scale scores were measured. Inattentiveness improved 2.6 points with St.Johns wort vs. 3.2 points with the placebo.
One group received a placebo. Why not just give this group no treatment at all?
Just thinking you are getting a treatment may have an effect, and we want to see if the real treatments do better than this.
Is St. John's wort effective in treating attention-deficit/hyperactivity disorder (ADHD) in children and adolescents? A report in a recent issue of the Journal of American Medical Association describes a study to answer this question
A randomized, double-blind, placebo-controlled trial was conducted involving 54 children aged 6 to 17 years. Participants were randomly assigned to receive 300 MG of St.Johns wort (27 Subjects) or matched placebo (27 subjects) 3 times daily for 8 weeks.
Results ADHD rating scale scores were measured. Inattentiveness improved 2.6 points with St.Johns wort vs. 3.2 points with the placebo.
The experiment was "double-blind" this means that
neither the subjects nor the people who worked with them knew whether they were taking St.Johns wort or Placebo
Is St. John's wort effective in treating attention-deficit/hyperactivity disorder (ADHD) in children and adolescents? A report in a recent issue of the Journal of American Medical Association describes a study to answer this question
A randomized, double-blind, placebo-controlled trial was conducted involving 54 children aged 6 to 17 years. Participants were randomly assigned to receive 300 MG of St.Johns wort (27 Subjects) or matched placebo (27 subjects) 3 times daily for 8 weeks.
Results ADHD rating scale scores were measured. Inattentiveness improved 2.6 points with St.Johns wort vs. 3.2 points with the placebo.
The subjects of the study included both girls and boys. All of the subjects were randomly assigned among all the treatments with one use of the table of random digits. This design is called.
A completely randomized design
Is St. John's wort effective in treating attention-deficit/hyperactivity disorder (ADHD) in children and adolescents? A report in a recent issue of the Journal of American Medical Association describes a study to answer this question
A randomized, double-blind, placebo-controlled trial was conducted involving 54 children aged 6 to 17 years. Participants were randomly assigned to receive 300 MG of St.Johns wort (27 Subjects) or matched placebo (27 subjects) 3 times daily for 8 weeks.
Results ADHD rating scale scores were measured. Inattentiveness improved 2.6 points with St.Johns wort vs. 3.2 points with the placebo.
The subjects of the study included both girls and boys. If the girls and boys were seperately assigned to treatments, using the table of random digits twice, the design would be
A block Design
An experiment compares two brands of automobile tires. Each of a number of cars is equipped with one tire of each brand on a rear wheel (the order is randomized from car to car) and tread wear is measured periodically. This is called
Matched pairs design
Is the new acne medication, Pimper Pulverizer, more effective than your current brand? You design an experiment to find out. A random sample of adolescents suffering from acne use the medication on one side of their face and the old medication on the other. Which side receives which medication is determined randomly. After two weeks, the difference in the severity of acne on the face of each subject is evaluated. What type of experiment design is this?
This is a matched pairs design
treatment 2 was a dummy pill. Such a dummy treatment is called a
Placebo
In order to avoid unconscious bias, neither the subjects not the doctors who examined them knew whether a particular subject was taking vitamins or a dummy pills. This is called
the double-blind technique
you work for advertising agency that is preparing a new television commercial to appeal to women. You have been asked to design an experiment to compare the effectiveness of three versions of the commercial. Each subject will be shown one of the three versions and then asked her attitude toward the product. You think there may be large differences between woman who are employed and those who are not. Because of these differences you should use.
a block design
An experiment compares the comfort of a t-shirt made with a new synthetic fiber with that of 100% cotton t-shirt. Each of a number of testers wears both shirts (in random order) and says which is more comfortably This is called a
Matched pairs design
A recent medical study found that people who drink more than four cups of coffee a day have more heart attacks than people who drink less coffee or no coffee. This led some doctors to suspect that coffee may be a contributing factor in causing heart attacks. However, more careful analysis of the data showed that heavy coffee drinkers tend to smoke more than other people. This is an example of
Confounding
In comparative trials in medicine, the placebo effect and subconscious bias on the part of the physicians evaluating treatment outcomes can be avoided by using
A double-blind Technique
;