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32 Cards in this Set
- Front
- Back
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Why is it so important that a statistical study use a representative sample? |
IF the sample fairly represents the population as a whole, then it is reasonable to make inferences from the sample to the population. |
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Briefly describe four common sampling methods. Choose the correct answer below. |
Simple random sampling; Systematic sampling; Convenience sampling; Stratified sampling |
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Identify the sampling method as simple random sampling, systematic sampling, convenience sampling, or stratified sampling. An IRS (Internal Revenue Service) auditor randomly selects for audits 1010 taxpayers in each of the filing status categories: single, head of household, married filing jointly, and married filing separately. |
Stratified sampling |
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What type of statistical study is most likely to lead to an answer to the following question? Is magnetic therapy a more effective way to treat headaches than Drug A or doing nothing at all? |
Experiment |
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A study of the academic preparation of high school language arts teachers used the teachers' mathematics scores on a standardized test for data. |
Yes, there is reason. Scores on standardized tests do not necessarily predict preparation. Yes, there is reason. The variables that were measured are not identified. Yes, there is reason. The study was about the preparation of language arts teachers, but uses the teachers' mathematics scores. |
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Sociologists studying domestic violence circulate a questionnaire asking each respondent if she or he has ever abused a spouse or partner. |
Yes, there is reason. Self-reporting is often not accurate. Yes, there is reason. The wording of the question might produce inaccurate or dishonest responses. Yes, there is reason. The people receiving the questionnaire might not be representative of the population. |
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An exit poll designed to predict the winner of a local election uses voluntary surveys with everyone who votes between 7am and 7:30 am |
Both selection and participation bias |
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What is the purpose of binning? Give an example in which binning is useful. |
The purpose of binning is to analyze the frequency of quantitative data grouped into categories that cover a range of possible values. A useful example is grouping quiz scores with a maximum score of 40 points with 10-point bins. The first bin contains scores 0-9, the second bin contains scores 10-19, and so on. |
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How can the graphics sometimes be misleading? |
The variation can seem to be larger than it really is. |
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How can the graphics sometimes be useful? |
It can make it easier to show small scale trends in the data. |
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There's been only a very slight rise in our stock price over the past few months, but I wanted to make it look dramatic so I started the vertical scale from the lowest price rather than from zero. |
The statement makes sense because reducing the range of the vertical axis to just fit the data will increase the relative size of the variation in the data. |
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Define positive correlation. Choose the correct answer below. |
Positive correlation means that both variables tend to increase (or decrease) together. |
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Define negative correlation. Choose the correct answer below. |
Negative correlation means that two variables tend to change in opposite directions, with one increasing while the other decreases. LONGEST ANSWER |
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Define no correlation. Choose the correct answer below. |
No correlation means that there is no apparent relationship between the two variables. |
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How do we determine the strength of a correlation? |
The more closely two variables follow the general trend, the stronger the correlation (which may be positive or negative). |
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Altitude on a mountain bike & air pressure |
there is a negative correlation because air pressure tends to increase when altitude decreases.
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When gasoline prices rise, sales of sport utility vehicles decline. |
NEGATIVE Correlation
This correlation is due to a possible direct cause because sport utility vehicles require more gasoline than a smaller type of vehicle. |
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Automobile gas mileage decreases with tire pressure. |
POSITIVE correlation This correlation is due to a direct cause because more gasoline is needed to roll a tire with lower pressure. |
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Choose the correct description of the mean below. |
The mean is the sum of all the values divided by the number of values. It can be strongly affected by outliers. |
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Choose the correct description of the median below. |
The median is the middle value in a data set. It is not affected by outliers. |
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Choose the correct description of the mode below. |
The mode is the most common value in a data set. It is not affected by outliers. |
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State, with an explanation, whether the mean, median, or mode gives the best description of the following average. The average number of times that people change jobs during their career? |
the MEDIAN Probably RIGHT SKEWED WITH A SINGLE PEAK |
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The standard deviation for the heights of a group of 5-year-old children is smaller than the standard deviation for the heights of a group of children who range in age from 3 to 15. |
The statement makes sense because the range of data for the heights of a group of 5-year-old children is smaller than the range of data for the heights of a group of children who range in age from 3 to 15. |
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A report claims that the returns for the investment portfolios with a single stock have a standard deviation of 0.52, while the returns for portfolios with 35 stocks have a standard deviation of 0.334. Explain how the standard deviation measures the risk in these two types of portfolios. |
A lower standard deviation means more certainty in the return and less risk. Hence, the returns for portfolios with 3535 stocks have less risk than the ones with a single stock. |
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Decide whether the following statement makes sense or does not make sense. The heights of male basketball players at a local college are normally distributed with a mean of 6 feet 3 inches and a standard deviation of 3 inches. |
Makes sense |
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State whether you would expect the following data set to be normally distributed or not. Scores on an easy statistics exam |
Not normally distributed |
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Decide whether the following statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain your reasoning. The study found that more people were cured by the new drug than by the old drug, but the result was not statistically significant. |
The statement makes sense. If the amount of the increase is small enough that it is likely to have occurred by chance, then the result would not be statistically significant. |
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At Linden High School there are math tests at the end of each three-month session. On all of the last 10 days when there was a math test at school, Brian got a cold and had to stay home. He didn't have colds at other times. |
Statistically significant |
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Do the following for the case below: a. State the null and alternative hypotheses for a hypothesis test. b. Describe the two possible outcomes of the test, using the context of the given situation. The governor claims that the percentage of adults over 21 who have graduated from high school is greater than 83%, the national average. What is the null? |
The percentage of adults over 21 who have graduated from high school is 83 %. |
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What is the alternative hypothesis? |
The percentage of adults over 21 who have graduated from high school is greater than 83% |
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What is the outcome if the null hypothesis is rejected? |
There is evidence that the percentage of high school graduates exceeds 83 %.83%.Your answer is correct.What is the outcome if the null hypothesis is not rejected? |
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What is the outcome if the null hypothesis is not rejected? |
There is insufficient evidence to conclude that the percentage of high school graduates exceeds 8383%. |
