stats
The GRE Exam (Graduate Record Examination) is widely used to help predict the performance of applicants to graduate schools. The Psychology Department of a university finds that its application on quantitative GRE are normally distributed with mean 544 and standard deviation 103. Suppose an applicant earns 492 on the quantitative GRE. What is the z-score (or standardized score) for this result? (Round your answer to one decimal place.)
-.5
Birth weights at a local hospital have a Normal distribution with a mean of 110 oz and a standard deviation of 15 oz. The proportion of infants with birth weights between 125 oz and 140 oz is: (Round your answer to three decimal places.)
.136
A company produces packets of soap powder labeled "Giant Size 32 Ounces." The actual weight of soap powder in such a box has a Normal distribution with a mean of 33 oz and a standard deviation of 0.7 oz. To avoid having dissatisfied customers, the company says a box of soap is considered underweight if it weighs less than 32 oz. What proportion of boxes is underweight (i.e., weigh less than 32 oz)? (Round your answer to four decimal places.)
.0766
Birth weights at a local hospital have a Normal distribution with a mean of 110 oz and a standard deviation of 15 oz. The proportion of infants with birth weights above 125 oz is: (Round your answer to three decimal places.)
.159
Scores on the SAT verbal test in recent years follow approximately the N(515, 109) distribution. The proportion of students scoring at least 600 is closest to: (Round your answer to three decimal places.)_
.218
A high-profile consulting company chooses its new entry-level employees from a pool of recent college graduates using a five-step interview process. Unfortunately, there are usually more candidates who complete the interview process than the number of new positions that are available. As a result, cumulative GPA is used as a tie-breaker. GPAs for the successful interviewees are Normally distributed with a mean of 3.3 and a standard deviation of 0.4. What proportion of candidates have a GPA under 3.0? (Round your answer to three decimal places.)_
.227
Scores on the SAT verbal test in recent years follow approximately the N(515, 109) distribution. The proportion of students scoring between 460 and 550 is closest to: (Round your answer to three decimal places.)
.319
The typical college freshman spends an average of µ = 150 minutes per day with a standard deviation of s=50 minutes on social media. The distribution of time on social media is known to be normal. The proportion of students spending at least 2 hours on social media equals: (Round your answer to three decimal places.)
.726
If a particular species of sharks always hunt prey that are 0.25 times as large as they are, what would the correlation between the sizes of sharks and their prey be? Question options: -1 -0.25 0.25 1
1
The average time taken for your Internet service provider to remotely resolve a trouble ticket has a Normal distribution with a mean of 4.3 hours and a standard deviation of 3.1 hours. What percent of the time can you expect to wait longer than a full (8-hour) business day for a resolution? (Round your answer to one decimal place.)
11.6
The typical college freshman spends an average of µ = 150 minutes per day with a standard deviation of s=50 minutes on social media. The distribution of time on social media is known to be normal. The median of the distribution is: (Round your answer to a whole number.)
150
Scores on a university exam are Normally distributed with a mean of 78 and a standard deviation of 8. The professor teaching the class declares that a score of 70 or higher is required for a grade of at least "C." Using the 68-95-99.7 rule, what percent of students failed to earn a grade of at least "C"?
16
The typical college freshman spends an average of µ = 150 minutes per day with a standard deviation of s= 50 minutes on social media. The distribution of time on social media is known to be normal. The upper quartile is: (Round your answer to two decimal places.)
183.72
group of four friends has a median age of 22. Three of them are ages 20, 18, and 24. The age of the fourth friend must be: 22 24 or older. 18 or younger. None of the above; we can't tell from the information provided.
24 or older.
The percent of observations above the third quartile in a large dataset is very close to
25
A high-profile consulting company chooses its new entry-level employees from a pool of recent college graduates using a five-step interview process. Unfortunately, there are usually more candidates who complete the interview process than the number of new positions that are available. As a result, cumulative GPA is used as a tie-breaker. GPAs for the successful interviewees are Normally distributed with a mean of 3.3 and a standard deviation of 0.4. Out of 163 people who made it through the interview process, only 121 can be hired. What cut-off GPA should the company use? (Round your answer to two decimal places.)
3.04
A company produces packets of soap powder labeled "Giant Size 32 Ounces." The actual weight of soap powder in such a box has a Normal distribution with a mean of 33 oz and a standard deviation of 0.7 oz. To avoid losing money, it labels the top 5% (the heaviest 5%) overweight. How heavy does a box have to be for it to be labeled overweight? (Round your answer to two decimal places.)
34.15
Which of the following sets of four numbers has the smallest standard deviation? 7, 8, 9, 10 5, 5, 5, 6 0, 0, 10, 10 0, 1, 2, 3
5, 5, 5, 6
A cappuccino vending machine is designed to dispense an average of µ oz per cup. If the ounces per fill are Normally distributed, with a standard deviation of 0.4 oz, what value should µ be set at so 6 oz cups will overflow only 2% of the time? (Round your answer to two decimal places.)
5.18
A violin student records the number of hours she spends practicing during each of nine consecutive weeks: 6.2 5.0 4.3 7.4 5.8 7.2 8.4 1.2 6.3 The data can be downloaded here. What is the mean number of hours spent practicing per week during this period? Round your answer to two decimal places.
5.76
Descriptive statistics for a set of test scores are shown above. For this test, a certain student has a z-score (standardized score) of z = -1.4. What score did this student receive? (Round your answer to two decimal places.)
551.84
A violin student records the number of hours she spends practicing during each of nine consecutive weeks: 6.2 5.0 4.3 7.4 5.8 7.2 8.4 1.2 6.3 What is the median number of hours spent practicing per week during this period? Round your answer to two decimal places.
6.2
A high-profile consulting company chooses its new entry-level employees from a pool of recent college graduates using a five-step interview process. Unfortunately, there are usually more candidates who complete the interview process than the number of new positions that are available. As a result, cumulative GPA is used as a tie-breaker. GPAs for the successful interviewees are Normally distributed with a mean of 3.3 and a standard deviation of 0.4. What percent of candidates have a GPA above 3.9? (Round your answer to one decimal place.)
6.7
Scores on the SAT verbal test in recent years follow approximately the N(515, 109) distribution. How high must a student score in order to place in the top 5% of all students taking the SAT? (Round to a whole number.)
694
What is the difference between a histogram and a bar chart? There is no difference. They are exactly the same. A histogram is a more accurate representation of a bar chart. A bar chart displays a qualitative variable on the horizontal axis, whereas a histogram does not. A bar chart displays a quantitative variable on the horizontal axis, whereas a histogram does not.
A bar chart displays a qualitative variable on the horizontal axis, whereas a histogram does not.
Which of the following statements is FALSE? Question options: Older men tend to have lower muscle density. Hence, the correlation between "age" and "muscle density" in older men must be negative. Older children tend to be taller than younger children. Hence, the correlation between "age" and "height" in children must be positive. A researcher finds the correlation between two variables is close to 0, so the two variables must be unrelated. Taller people tend to be heavier than shorter people, so the correlation between "height" and "weight" must be positive.
A researcher finds the correlation between two variables is close to 0, so the two variables must be unrelated.
whats a variable in data
A variable is any characteristic of an individual. A variable can take different values for different individuals.
A Normal distribution: Question options: is symmetric. can be completely specified by a mean, µ and a standard deviation, s. has an area of exactly 1 underneath the density curve. All of the answer options are correct.
All of the answer options are correct.
A scatterplot of the amount of alcohol consumed according to a food diary (DR) against the amount of alcohol consumed on a frequent food questionnaire (FFQ): Question options: shows the relationship between the answers from the food diary and the FFQ. assesses if the relationship between the answers on the DR and FFQ is positive. shows for each study participant the answers they gave on the FFQ and DR. All of the answer options are correct.
All of the answer options are correct.
As part of a data base of new births at a hospital, some variables recorded are the age of the mother, marital status of the mother (e.g., single, married, divorced), weight of the baby, and sex of the baby. Of these variables: the individuals described are mothers and babies involved in births at a hospital. age of mother and weight of baby are quantitative variables. sex and marital status are qualitative variables. All of the answer options are correct.
All of the answer options are correct.
Colleges often rely heavily on raising money for an "annual fund" to support operations. Alumni are typically solicited for donations to the annual fund. Studies suggest that the graduate's annual income is a good predictor of the amount of money he or she would be willing to donate, and there is a reasonably strong, positive, linear relationship between these variables. In the studies described: Question options: annual income is an explanatory variable. the correlation between annual income and size of donation is positive. size of donation to the annual fund is the response variable. All of the answer options are correct.
All of the answer options are correct.
Following are some of the variables from a survey conducted by the U.S. Census Bureau. Which of the variables is quantitative? the number of people living in a household the total household gross income the ages of household residents All of the answer options are correct.
All of the answer options are correct.
Which of the following is TRUE of the correlation coefficient r ? Question options: Multiplying all data values (x's and y's) by 20 will have no impact on r. -1 ≤ r ≤ +1 If r = 0, then there is no linear relationship between x and y. All of the answer options are correct.
All of the answer options are correct.
Which of the following statements is CORRECT? Question options: Changing the units of measurements of x or y does not change the value of the correlation r. A negative value for the correlation r indicates the data are strongly unassociated. The correlation always has the same units as the x variable but not the y variable. The correlation always has the same units as the y variable but not the x variable.
Changing the units of measurements of x or y does not change the value of the correlation r.
name variable type: cholesterol concentration
Continuous quantitative
name variable type: length
Continuous quantitative
name variable type: time
Continuous quantitative
name variable type: weight
Continuous quantitative
What can be said of the correlation between the brand of an automobile and its quality? Question options: The correlation is negative because smaller cars tend to have higher quality, and larger cars tend to have lower quality. The correlation is positive because better brands have higher quality. If correlation is negative, an arithmetic mistake was made. Correlation must be positive. Correlation makes no sense here because "brand" is a categorical variable.
Correlation makes no sense here because "brand" is a categorical variable.
For a categorical variable, we can use which of the following numerical summaries? (Note you can select more than one.) Means Medians Counts Percents IQR
Counts Percents
name variable type: age in years
Discrete quantitative
name variable type: number of bacteria, trees, leaves, etc
Discrete quantitative
what are individuals in data
Individuals are the objects described by a set of data. Individuals may be people, animals, or things.
Definition of density curve
Must lie on or above the horizontal axis,Must have area exactly 1 underneath curve,Area under the curve for any range of x-values is equal to the proportion of all observations that fall in that rang
name variable type: •color of a flower
Qualitative nominal
name variable type: •gender
Qualitative nominal
name variable type: •shape of a seed
Qualitative nominal
name variable type: blood type
Qualitative nominal
name variable type:
Qualitative ordinal variable
name variable type: cloudiness:overcast, mostly cloudy, partly cloudy, sunny
Qualitative ordinal variable
name variable type: month of the year: 1,2,3,4,5,6,7,8,9,10,11,12
Qualitative ordinal variable
name variable type: patient response to an exam: worse, somewhat worse, the same, improvement
Qualitative ordinal variable
A description of different houses on the market includes the variables square footage of the house and average monthly gas bill. Which of the following statements is true? Square footage and average monthly gas bill are both qualitative variables. Square footage and average monthly gas bill are both quantitative variables. Square footage is a qualitative variable and average monthly gas bill is quantitative variable. Square footage is a quantitative variable and average monthly gas bill is qualitative variable.
Square footage and average monthly gas bill are both quantitative variables.
A spokesperson for the Bureau of Economic Research reported to the Council of Economic Advisers the following information: "We found that the correlation between the duration (in months) of business cycles' expansions and the duration (in months) of business cycles' contractions was 0.25 years." This statement contains a mistake. Can you tell which? Choose one answer. Question options: The correlation coefficient measures only direction and strength, not duration. The two variables compared are not both quantitative. The correlation coefficient doesn't have units. The correlation coefficient cannot be that small.
The correlation coefficient doesn't have units.
Which of the following statements is FALSE? Question options: The correlation coefficient equals the proportion of data points that lie on a straight line. The correlation coefficient will be +1.0 only if all the data lie on an upward-tilting straight line. The correlation coefficient is undefined if all the data lie on a perfectly horizontal straight line. The correlation coefficient is a unitless number and must always lie between -1.0 and +1.0, inclusive.
The correlation coefficient equals the proportion of data points that lie on a straight line.
subjects and experimenters dont know if they are in an experiment
double binding randomized control
the way the survey is worded
Wording bias
A political party's data bank includes the zip codes of past donors such as 47906 34236 53075 10010 90210 75204 30304 99709 Zip codes is a quantitative variable. a qualitative variable neither a qualitative nor quantitative variable. a unit of measurement.
a quantitative variable.
discrete or continuous: variable is one where at least in principle the values could be any possible value on a scale.
continuous quantitative
weight, length, time (decimals, halves, etc)
continuous quantitative
A researcher states that bone density in women is negatively associated with age. This means that: Question options: as women get older, bone density tends to decrease. as women get older, bone density tends to increase. below-average values of age tend to accompany below-average values of bone density. older women aren't any more likely than younger women to have below-average bone density.
as women get older, bone density tends to decrease.
AGE, NUMBER OF
discrete quantitative
discrete or continuous: variable is where the values only be discrete points on a scale
discrete quantitative
To display the distribution of grades (A, B, C, D, F) for all students in a course, it would be correct to use a pie chart but not a bar graph a bar graph but not a pie chart either a pie chart or bar graph a histogram
either a pie chart or bar graph
An _________ variable may explain changes in the response variable.
explanatory (or independent)
quantitative data is summarized graphically by using
histograms and stem plots
A study was set up to determine if there was an association between music in utero and time of advancement to crawling/walking in infants. In the study infants listened to three types of 'music' in utero and their advancement to crawling/walking was then observed and categorized as either early, on time, or late. To study this association, we would: Question options: make a scatterplot and calculate a correlation coefficient make calculations using a two-way table make a scatterplot calculate a correlation coefficient
make calculations using a two-way table
Measures of the center
mean median
a probability sampling technique involving at least two stages: a random sample of clusters followed by a random sample of people within the selected clusters- used by gov
multistage sampling
nominal or ordinal... variable is one where there is no ordering.
nominal
blood type, gender, color, shape
nominal qualitative
People who feel they have something to hide or who don't like their privacy being invaded probably won't answer. Yet they are part of the population.
nonresponse bias
the median age of five people in a meeting is 30 years. One of the people, whose age is 50 years, leaves the room. The median age of the remaining four people in the room is: 40 years. 30 years. 25 years. not able to be determined from the information given.
not able to be determined from the information given.
Are higher than average sea surface temperatures associated with a greater than average number of hurricanes each year? In a 2010 study, the average global sea surface temperature anomaly was recorded, along with the number of Atlantic hurricanes above or below the average for that year. The response variable is: Question options: number of hurricanes above or below average. the global sea surface temperature anomaly. the number of hurricanes used in the study. None of the answer options is correct.
number of hurricanes above or below average.
what type of sampling: observing ppl who already have a treatment
observational
nominal or ordinal.... variable is one where there is a natural ordering to the categories
ordinal
Strongly agree to strongly disagree, partly cloudy
ordinal qualitative
categorical data is summarized graphically by using
pie charts and bar charts
Archaeologists often find only parts of ancient human remains. For example, they may find a small finger bone, called the metacarpal bone. Is it possible to predict the height of a human from the length of his or her metacarpal bone? To investigate, a researcher measures the heights and metacarpal lengths of 200 adults. In making the scatterplot, the researcher should: Question options: plot the height of the person on the horizontal axis. plot the metacarpal length on the horizontal axis. first determine if the heights of humans follow a Normal distribution. use a plotting scale that makes the overall trend roughly linear. Question 7 1 / 1 point
plot the height of the person on the horizontal axis.
what variable places an individual into one of several groups or categories?
qualitative or categorical
Employees at a large company are surveyed about their health insurance status. Employees are coded as "1" if health insurance is obtained through the company's benefit program, "2" if health insurance is obtained from another source (e.g., through a spouse's employment benefit program), or "0" if the employee does not have health insurance. This variable is: quantitative. qualitative. neither.
qualitative.
Relationships require that both variables be
quantitative
what type of sampling: experimenter gives random people a treatment
random
Measures of spread or variation
range quartiles (interquartile range) variance standard deviation
A_______ variable measures or records an outcome of a study
response (or dependent)
Questions about the past or sensitive issues often get biased responses , or uninformed
response bias
things you need to describe a histogram
shape, what type of , modal, what it ranges from, outliers?, and mode
every member of the population has a known and equal chance of selection
simple random sample
subjects dont know if they are in an experiment
single binding randomized control
1 / 1 point You look at real estate ads in Naples, Florida. There are many houses ranging from $200,000 to $500,000 in price. the few houses on the water, have prices up to $15 million. The distibution of house prices will be skewed to the left. roughly symmetric. skewed to the right.
skewed to the right.
A form of probability sampling; a random sampling technique in which the researcher identifies particular demographic categories of interest and then randomly selects individuals within each category.
stratified random sampling
The _________ of the relationship between the two variables can be seen by how much variation, or scatter, there is around the m
strength
A company has three divisions and three conference rooms for meetings. To keep track of the use of their facilities, for each meeting held in the company, the division holding the meeting is recorded, the room for the meeting is recorded, and the length of time of the meeting is recorded. Which of the variables is quantitative? the division holding the meeting the conference room for the meeting the length of time for the meeting All of the answer options are correct.
the length of time for the meeting
Which of the following is likely to have a mean that is smaller than the median? a.the salaries of all National Football League players, where a few players make much more than most players the scores of students (out of 100 points) on a very easy exam in which most scores are high, but a few scores are low the prices of homes in a large city, where there are lots of relatively inexpensive homes and a few very expensive homes the scores of students (out of 100 points) on a very difficult exam in which most scores are low, but a few scores are high
the scores of students (out of 100 points) on a very easy exam in which most scores are high, but a few scores are low
A researcher calculates the correlation coefficient between two variables. This correlation coefficient tells us: Question options: whether there is a relation between two variables. whether a scatterplot shows an interesting pattern. whether a cause-and-effect relation exists between two variables. the strength and direction of a linear association between two variables.
the strength and direction of a linear association between two variables.
A scatterplot can be used to illustrate the relationship between: Question options: two categorical variables. one categorical variable and one quantitative variable. two quantitative variables. All of the answer options are correct.
two quantitative variables.
occurs when some groups in the population are left out of the process of choosing the sample
undercoverage bias
bias introduced to a sample when individuals can choose on their own whether to participate in the sample
voluntary response bias
A description of different houses for sale includes the following variables. Which of the variables is qualitative (or categorical)? the square footage of the house whether or not the house has a finished basement the monthly electric bill
whether or not the house has a finished basement
There are three children in a room, ages 3, 4, and 5. If the 4 year old enters the room, the mean age: will stay the same, but the variance will increase. will stay the same, but the variance will decrease. and variance will stay the same. and variance will increase.
will stay the same, but the variance will decrease.
When there is an obvious explanatory variable, it is plotted on the
x axis.
My expectations for a good description of the histogram of a data set:
•Describe the shape of the histogram using the standard language described above. •Describe the spread by giving the values of the lowest and highest data values. This is known as the "spread." •Give the location of the modes (or modes if the data is bimodal or trimodal). •Discuss any outliers (values that are extreme or don't fit the overall pattern)