Stats 1430 Midterm

A two-way table allows us to examine the relationship between categorical variables. A. True B. False

A

Bob wants to do a telephone survey based on 100 people. Knowing that some people won't answer the phone, so 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 continues this way until he gets 100 responses. Will this sampling method create bias in Bob's data? A. Yes B. No

A

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? A. For every additional square foot, we expect a home's selling price to increase by $33.80 B. For every additional square foot, we expect a home's selling price to increase by $5,240 C. For every additional dollar of selling price, we expect a homes square footage to increase by $33.80 D. There is not enough information to decide

A

If you switch X and Y the sign of the correlation changes A. True B. False

B

Which of the following is the complement of "at most 1"? A. None of the above B. "Less than 1" C. "More than 1" D. "At least 1"

C

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. A. True B. False

A

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? A. Yes B. No C. Not enough information to tell

A

If A and B are independent, all you need is P(A) and P(B) to calculate P(A or B). A. True B. False

A

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. A. True B. False

A

Changing the number of bins will never change the shape of a histogram A. True B. False

B

Suppose 40% of all OSU students own a tablet PC and an iPhone. Write this as a probability A. P(Table PC | iPhone) = 0.40 B. None of the above C. P(iPhone | Table PC) = 0.40

B

The units of r, the correlation coefficient, are the same as the X variable. A. True B. False

B

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 A. True B. False

B

Which of the following summary measures can be directly calculated from a box plot? A. Sample size B. Standard deviation C. IQR D. Mean

C

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? A. None of the above B. The microwave C. Brand of popcorn D. Time setting

D

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? A. 100% B. Can't find, or not enough information C. 40% D. 24%

D

Suppose a school figures that 70% of adults will purchase a candy bar from a 6th grader during a fundraiser. A 6th grader randomly selects 10 adults, what's the chance that at least one of them will buy a candy bar? A. 1-(0.70^10) B. 0.70^10 C. (1-0.70)^10 D. None of the above

D

Which of the following best describes a confounding varaible? A. A variable you included in the study that had no effect on the results B. All of the above C. A variable you included in the study that did have an effect on the results D. A variable you did not include in the study that may have had an effect on the results

D

Which of the following is NOT one of the criteria for a good experiment as described in lecture? A. Avoid or minimize bias B. Collect enough data C. Make comparisons D. Select a random sample of individuals to participate

D

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? A. Bayes' Rules B. Simpson's Paradox C. Law of Total Probability D. The answer is one of the numbers given in the problem-no method needed

A

Your boss gives you the following regression equation. Selling price=$5,240+$33.80(number of square feet). The residuals have units of dollars. A. True B. False

A

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? A. 36% B. 42% C. 90% D. Not enough information

A

Suppose 70% of Facebook users have Twitter accounts. Write this as a probability. A. P(Twitter | Facebook) = 0.70 B. P(Twitter and Facebook) = 0.70 C. P(Facebook | Twitter) = 0.70

A

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 A. True B. False

A

Suppose your data represents 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. A. True B. False

A

The mean is influenced by outliers (values that are much larger or much smaller than the rest of the data.) A. True B. False

A

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? A. Yes B. No C. Not enough information to tell

B

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. A. True B. False

B

If a data set is skewed to the left, how will the mean and median compare? A. The mean will be the same as the median B. The mean will be less than the median C. The mean will be greater than the median

B

If the conditional distribution is different from the corresponding marginal distribution in a two-way table, we know that the variables are NOT related. A. True B. False

B

If the correlation coefficient, r, between two variables is 0, we can conclude that there is no relationship between the two variables. A. True B. False

B

If you add 10 to every value of a data set, which of the following will also increase by 10? A. The mean B. Both the median and mean will increase by 10 C. Neither the median nor the mean will increase by 10 D. The median

B

Outliers significantly affect the value of the median A. True B. False

B

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? A. +0.80 B. +0.25 C. -0.10 D. -0.90

D

In thinking about the 5-number summary, the percentage of data below Q1 AND Q3 combined is the same as the percentage of data in the IQR A. True B. False

A

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? A. Experiment B. Observational study

B

A CONDITIONAL distribution summaries the information from one variable ONLY, without considering ANY information from another variable. A. True B. False

B

A flat histograms contains no variability whatsoever, according to our definition A. True B. False

B

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? A. Yes, because income and total purchase amount are categorical variables B. Yes, because income and total purchase amount are quantitative variables C. No, because income and total purchase amount are categorical variables D. There is not enough information to decide

B

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. A. True B. False

B

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? A. There is not enough information to answer this question B. There is a moderately strong negative linear relationship between temperature and latitude. C. There is a moderately strong relationship between temperature and latitude D. There is a moderately strong negative relationship between temperature and latitude

B