Stats 1430 Quizzes: Midterm Review
Thomas wants to know what percentage of females buy his product. Thomas knows his customers are 50% male and 50% female, and that 30% of all his customers buy his product. He collects data on people who have already bought his product, and asks their gender. He finds that 70% of the people who bought his product were female. What method would you use to answer Thomas' original question?
Bayes Rule
If you add 10 to every value of a data set, which of the following will also increase by 10?
Both the median and mean will increase by 10.
A conditional distribution summaries the information from one variable ONLY, without considering ANY information from another variable.
False
A flat histogram contains no variability whatsoever, according to our definition.
False
A researcher is trying to determine the January temperature in regions of the United States using the degrees of latitude. After collecting data, she creates a scatterplot. Given the relationship the researcher is trying to predict, the latitude is the dependent variable and the temperature is the independent variable.
False
Boxplot A and Boxplot B are drawn on the same axes. If Boxplot A is shorter in length than boxplot B, it also has to contain less data than Boxplot B.
False
Changing the number of bins will never change the shape of a histogram.
False
If the conditional distribution is different from the corresponding marginal distribution in a two-way table, we know that the variables are NOT related.
False
If the correlation coefficient, r, between two variables is 0, we can conclude that there is no relationship between the two variables.
False
If you switch X and Y the sign of the correlation changes.
False
Outliers significantly affect the value of the median.
False
Suppose the correlation between X =price of a gallon of gaspline and Y = price of a gallon of milk is r = .40. Then the correlation between the price of a HALF gallon of milk and the price of a HALF gallon of gas must be r = .4/2 = .20.
False
The units of r, the correlation coefficient, are the same as the X variable.
False
Your boss gives you the following regression equation. Selling price = $5,240 + $33.80 (Number of Square Feet). It makes sense to interpret the Y-intercept for this equation.
False
Your boss gives you the following regression equation. Selling price = $5,240 + $33.80 (Number of Square Feet). What is the correct interpretation of the slope of this equation?
For every additional square foot, we expect a home's selling price to increase by $33.80.
Which of the following summary measures can be directly calculated from a boxplot?
IQR
Bob and Bill live in an apartment together. Bob is in the apartment 30% of the time overall. But when Bill is in the apartment, Bob is only there 10% of the time. Let Event A = "Bill is in the apartment", and let Event B = "Bob is in the apartment." Are Events A and B independent?
No
A veterinarian collects data on 100 of his patients who come in every year for their annual check-ups. After 5 years, he compares the health status of the dogs to the cats. What type of study is this?
Observational Study
Suppose 70% of Facebook users have Twitter accounts. Write this as a probability.
P(Twitter | Facebook) = 0.70
Which of the following is not one of the criteria for a good experiment as described in lecture?
Select a random sample of individuals to participate
Suppose A and B are disjoint. Then P(A|B) = 0.
TRUE
Which of the following is the complement of "at most 1"?
"more than 1"
Suppose you have 4 data sets whose scatterplots all show possible linear relationships. The four data sets have correlations of -0.10, +0.25, -0.90, and +0.80, respectively. Which of the correlations shows the strongest linear relationship?
-0.90
Suppose 40% of OSU students have internships over the summer, and of those who have internships, 60% of them are business majors. What percentage of all OSU students are business students and have internships over the summer?
24%
Suppose a school figures that 70% of adults will purchase a candy bar from a 6th grader during a fund-raiser. A sixth grader randomly selects 10 adults. What's the chance that at least one of them will buy a candy bar?
none of the above
Suppose 40% of all OSU students own a Tablet PC and an iPhone. Write this as a probability.
none of the above: P(Tablet & iPhone) = 40%
Suppose 20% of OSU students are business majors, and of the business majors, 60% have internships over the summer. Of those who are not business majors, 30% have internships over the summer. What percentage of ALL students have internships over the summer?
36%
A manager of a retail store is interested in the relationship between a person's annual income and their total purchase amount. Could he measure this relationship by finding the correlation?
Yes, because income and total purchase amount are quantitative variables.
Which of the following best describes a confounding variable?
A variable you did not include in the study that may have had an effect on the results.
Which of the following combinations of variables would be appropriate to examine with a scatterplot?
Age and Salary
If a data set is skewed to the left, how will the mean and median compare?
The mean will be less than the median.
A researcher is trying to determine the January temperature in regions of the United States using the degrees of latitude. After collecting data, she creates the scatterplot above. Which of the following is the correct interpretation of the correlation depicted in the scatterplot?
There is a moderately strong negative linear relationship between temperature and latitude.
An experimenter compares a single brand of popcorn to see how much popcorn is popped using different time settings on the same microwave. The time settings are 1.5 minutes, 2 minutes, 2.5 minutes, and 3 minutes. In this situation, what is the factor?
Time Setting
A STAT 1430 student is interested in examining the relationship between the number of bedrooms in a home and it's selling price. After downloading a valid data set from the internet, the student creates a scatterplot and calculates the correlation. The correlation value they calculate is 0.67. This implies that the selling price of a house tends to increase as the number of bedrooms increases.
True
A two-way table allows us to examine the relationship between categorical variables.
True
If A and B are independent, all you need is P(A) and P(B) to calculate P(A or B).
True
If there are a few very large values in a data set compared to the rest of the data, the mean will be larger than the median.
True
In thinking about the 5-number summary, the percentage of data below Q1 and above Q3 combined is the same as the percentage of data in the IQR.
True
Suppose the equation Y = 3.45 - 2.58 (X) represents a valid regression equation: From this information, we know that X and Y have a negative correlation.
True
Suppose your data represent revenues from a group of 20 stores in a retail chain across the country, and revenue is measured in millions of dollars. The first quartile of this data set would also be measured in millions of dollars.
True
The mean is influenced by outliers (values that are much larger or much smaller than the rest of the data.)
True
Your boss gives you the following regression equation. Selling price = $5,240 + $33.80 (Number of Square Feet). The residuals have units of dollars.
True
Bob wants to do a telephone survey based on 100 people. Knowing that some people won't answer the phone, he selects a random sample of 200 names to be safe, so if someone isn't home, he can just call the next person on the list. He continue this way until he gets 100 responses. Will this sampling method create bias in Bob's data?
Yes
If 60% of male-owned businesses are successful in their first year, and 60% of female-owned businesses are successful in their first year, are gender and having a successful business in their first year independent?
Yes
