STATS
What is a scatterplot and how does it help us?
A scatterplot is a graph of paired (x, y) quantitative data. It provides a visual image of the data plotted as points, which helps show any patterns in the data.
Examine the list of birth weights to make an observation about those numbers. How does that observation affect the way that the results should be rounded?
All of the weights end in 00, so they all appear to be rounded to the nearest 100 grams. This suggests that the mean and median should also be rounded.
Listed below are the highest amounts of net worth (in millions of dollars) of all celebrities. What do the results tell us about the population of all celebrities? Based on the nature of the amounts, what can be inferred about their precision?
Apart from the fact that all other celebrities have amounts of net worth lower than those given, nothing meaningful can be known about the population., The values all end in 0 or 5, so they appear to be rounded estimates.
Which of the following is NOT one of the three common errors involving correlation?
Correlation does not imply causality
Are the data reported or measured?
The data appears to be measured. The heights occur with roughly the same frequency.
In a study designed to test the effectiveness of a medication as a treatment for lower back pain, 1643 patients were randomly assigned to one of three groups: (1) the 547 subjects in the placebo group were given pills containing no medication; (2) 550 subjects were in a group given pills with the medication taken at regular intervals; (3) 546 subjects were in a group given pills with the medication to be taken when needed for pain relief. In what specific way was replication applied in the study?
The group sample sizes are all large so the researchers could see the effects of the treatment.
Listed below are the jersey numbers of 11 players randomly selected from the roster of a championship sports team. What do the results tell us?
The jersey numbers are nominal data and they do not measure or count anything, so the resulting statistics are meaningless.
How does the stem-and-leaf plot show the distribution of these data?
The lengths of the rows are similar to the heights of bars in a histogram; longer rows of data correspond to higher frequencies.
If we collect a large sample of blood platelet counts and if our sample includes a single outlier, how will that outlier appear in a histogram?
The outlier will appear as a bar far from all of the other bars with a height that corresponds to a frequency of 1.
Listed below are the weights in pounds of 11 players randomly selected from the roster of a championship sports team. Are the results likely to be representative of all players in that sport's league?
The results are not likely to be representative because the championship team may not be representative of the entire league.
Listed below are selling prices (dollars) of TVs that are 60 inches or larger and rated as a "best buy" by a popular magazine. Are the resulting statistics representative of the population of all TVs that are 60 inches and larger? If you decide to buy one of these TVs, what statistic is most relevant, other than the measures of central tendency?
The sample consists of the "best buy" TVs, so it is not a random sample and is not likely to be representative of the population.; The lowest price is a relevant statistic for someone planning to buy one of the TVs.
In a double-blind experiment designed to test the effectiveness of a new medication as a treatment for lower back pain, 1643 patients were randomly assigned to one of three groups: (1) the 547 subjects in the placebo group were given pills containing no medication; (2) 550 subjects were in a group given pills with the new medication taken at regular intervals; (3) 546 subjects were in a group given pills with the new medication to be taken when needed for pain relief. WHAT DOES IT MEAN A DOUBLE-BLIND EXPERIMENT
The subjects in the study did not know whether they were taking a placebo or the new medication, and those who administered the pills also did not know.
In this section we use r to denote the value of the linear correlation coefficient. Why do we refer to this correlation coefficient as being linear?
The term linear refers to a straight line, and r measures how well a scatterplot fits a straight-line pattern.
Which of the following statements about correlation is true?
We say that there is a positive correlation between x and y if the x-values increase as the corresponding y-values increase.
a research company uses a device to record the viewing habits of about 7500 households, and the data collected over the next 8 years will be used to determine whether the proportion of households tuned to a particular childrens program decreases
a prospective study
r is a
a statistic that represents the value of the linear correlation coefficient computed from the paired sample data, and rhoρ is a parameter that represents the value of the linear correlation coefficient that would be computed by using all of the paired data in the population of all statistics students.
A women is selected by a company to participate in a focus group. She was selected because everyone in 5 randomly selected towns was being selected. What kinda sampling?
cluster sampling
A __________ exists between two variables when the values of one variable are somehow associated with the values of the other variable.
correlation
researcher plans to obtain data by interviewing spouses of victims who died in a tornado to see how their coping
cross-sectional study
The value of r
does not change, because r is not affected by converting all values of a variable to a different scale.
The heights of the bars of a histogram correspond to _______ values.
frequency
We utilize statistical _______ to look for features that reveal some useful or interesting characteristics of the data set.
graphs
Which of the following is NOT a requirement in determining whether there is a linear correlation between two variables?
if r>1, then there is a positive linear correlation.
Years of elections: 1988, 1990, 1992, 1994, and 1996
interval
eye color of respondents is 10 brown, 5 green, 2 blue
nominal
companies that produced movies in 2009
nominal level of measurement is most appropriate because the data can't be ordered.
survey respondents of yes, no and no opinion
nominal level of measurement is most appropriate because the data can't be ordered.
course grade from A-F
ordinal level, data can be ordered but differences cannot be found or is meaningless
critic rating of 1-5 stars
ordinal level, data can be ordered but differences cannot be found or is meaningless
890 adults were called after their telephone numbers were randomly generated by a computer, and 78% were able to correctly identify the attorney general
random sampling
If we have a large voluntary response sample consisting of weights of subjects who chose to respond to a survey posted on the Internet, can a graph help to overcome the deficiency of having a voluntary response sample?
No, a graph cannot help to overcome the deficiency. If the sample is a bad sample, there are no graphs or other techniques that can be used to salvage the data.
A magazine published a list consisting of the state tax on each gallon of gas. If we add the 50 state tax amounts and then divide by 50, we get 27.3 cents. Is the value of 27.3 cents the mean amount of state sales tax paid by all U.S. drivers? Why or why not?
No, the value of 27.3 cents is not the mean because the 50 amounts are all weighted equally in the calculation, but some states consume more gas than others, so the mean amount of state sales tax should be calculated using a weighted mean.
A _______ is a plot of paired data (x,y) and is helpful in determining whether there is a relationship between the two variables.
scatterplot
When determining whether there is a correlation between two variables, one should use a ____________ to explore the data visually.
scatterplot
researcher selcts every 461 social number
systematic sampling
In general, what is a problem with a very low response rate?
It creates a serious potential for getting a biased sample that consists of those with a special interest in the topic.
If we find that there is a linear correlation between the concentration of carbon dioxide in our atmosphere and the global temperature, does that indicate that changes in the concentration of carbon dioxide cause changes in the global temperature?
No. The presence of a linear correlation between two variables does not imply that one of the variables is the cause of the other variable.
Listed below are the annual tuition amounts of the 10 most expensive colleges in a country for a recent year. What does this "Top 10" list tell us about the population of all of that country's college tuitions?
Nothing meaningful can be concluded from this information except that these are the largest tuitions of colleges in the country for a recent year.
A particular country has 45 total states. If the areas of all 45 states states are added and the sum is divided by 45, the result is 1000 km.
PARAEMETER
study conducted of all 10000 workers in a state
PARAMETER, POP
In a study of all 3999 professors at college, 25% own a TV
PAREMETER, POPULATION
A homeowner measured the voltage supplied to his home on all 365 days in a year , and the average(mean) value is 130 volts
Parameter, population
A country has 55 states. If states added and sum divided by 50, result is 100000 km.
STATISTIC, SAMPLE
homeowner measured voltage on 50 days, the average was 121.4 volts
STATISTIC, SAMPLE
Listed below are foot lengths in inches of randomly selected women in a study of a country's military in 1988. Are the statistics representative of the current population of all women in that country's military?
Since the measurements were made in 1988, they are not necessarily representative of the current population of all women in the country's military.
monthly rain fall: 3.4 in, 3.5 in. 4 in, 4.5 in
ratio
movie with 4 star rating is twice as good as one with 2 star rating
ratio level doesn't apply
people's ages
ratio, because data can be ordered, difference can be found and is meaningful, and natural 0 starting point.
