Stats Midterm Practice Exam Questions

True or false: IQR is affected by outliers.

False

True or false: There are different amounts of data in each section of a boxplot.

False

True or false: There can be different amounts of data in each section of a boxplot.

False

True or false: You can always interpret both the slope and the Y-intercept of the regression line.

False

True or false: You can tell how much data there is in a data set by looking at its boxplot.

False

True or false: Correlation is affected by outliers and skewness.

True

True or false: If you multiply every single number in a data set by the same value, the standard deviation is also multiplied by that same value.

True

True or false: If you switch X and Y the slope and Y-intercept of the regression line will change.

True

True or false: In a histogram, the horizontal (X) axis is the variable you are measuring, and the vertical (Y) axis is the number or percentage of individuals in each group.

True

How do we use correlation and coefficient of determination (R-squared?) a. R-squared measures any kind of relationship; correlation only measures linear relationships. b. R-squared measures only linear relationships; correlation only measures linear relationships. c. R-squared measures only linear relationships; correlation measures any kind of relationship. d. R-squared measures any kind of relationship; correlation measures any kind of relationship.

A

If A and B are independent events with P(A) = 0.20 and P(B) = 0.60, then P(A|B) is: a. 0.20 b. 0.60 c. 0.12 d. None of the above /Can't tell without more information.

A

Which type of distribution shows the overall percentage in each of the 4 cells of a two-way table? a. Joint distribution b. Marginal distribution c. Conditional distribution

A

A list of the data that occurred in a data set and how often it occurred is called what? a. A data frequency b. A data distribution c. A relative frequency d. Quantitative data

B

Which type of probabilities are in each of the 4 cells of a two-way table of probabilities? a. Conditional probabilities b. "And" probabilities c. Marginal probabilities d. None of the above

B

If r = .81, what is the value of the coefficient of determination? a. .81 b. .90 c. .66

C

Suppose 80% of students wear backpacks. You randomly choose 2 students. What is the chance that exactly one of them is wearing a backpack? a. 0.80 b. 0.16 c. 0.32 d. None of the above

C

True or False: A survey has 1,000 responses. This is a high quality survey because the number of responses is high, no matter how many people were surveyed in the first place.

False

True or False: An anonymous survey is one in which they can link you to your data but they promise that they won't do so.

False

True or False: If the correlation is 0 you know there is no relationship between X and Y.

False

True or false: A confidential survey is one in which they cannot link you to your data.

False

True or false: A confounding variable is a variable that was accounted for in an experiment.

False

True or false: A flat histogram has zero variability.

False

True or false: An influential point is defined to be a point with a large residual.

False

True or false: For A and B to be independent, we need P(A|B) to equal P(Ac|B).

False

True or false: If a point has a negative residual that means the point lies above the line.

False

True or false: If you add the same value to every single number in a data set, the standard deviation also changes by that same value.

False

True or false: No two histograms share the same boxplot unless the histograms are the same.

False

True or False: The wording of a question can affect the results.

True

True or false: A and Ac are disjoint events. (Hint: what does it mean for events to be disjoint?)

True

True or false: A confounding variable can cause the results of a two-way table to reverse when it is added to the data set.

True

True or false: Suppose you know the mean of a data set and the data set has five numbers. If you know four of the numbers and the mean, you can determine the fifth number in the data set.

True

If you are comparing two conditional distributions, (for example Purchase Given Saw the Ad compared to Purchase given Didn't See the Ad), and the results are the same, what do you conclude?

independent

If P(A) = .2, P(B) = .3, and P(A|B) = .1, what is P(A and B)? a. .06 b. .1 c. .02 d. .03 e. None of the above

D

If you switch X and Y, which of the following will change? a. The correlation b. The slope of the regression line c. The Y-intercept of the regression line d. Both b and c will change e. All of a, b, and c will change

D

The correlation between study time for an exam (in minutes) and exam score is 0.79. If we convert study time to hours, the correlation will: a. Increase by a factor of 60 b. Decrease by a factor of 60 c. Switch signs to become -0.79 d. Stay the same

D

Which of the following is NOT in the same units as the original data? a. standard deviation b. Q1 c. y-intercept of the regression line d. All of the above are in the same units as the original data.

D

If there is no relationship between two variables in a two-way table, then the two variables are said to be: a. Independent b. Dependent (also known as Not Independent) c. Not enough information to tell.

A

If there is no relationship between two variables, then the two variables are said to be: a. Independent b. Not independent c. Not enough information to tell.

A

SSE is equal to what? a. The Sum of Squares for Error for any line going through the data. b. The Sum of Squares for Error for only the best line going through the data.

A

Suppose P(A) = .2 and P(A|B) = .2 so A and B are independent. Find P(A|Not B). a. .2 b. .8 c. .04 d. Can't find this probability with the information given

A

What do we call the four cells inside of a two-way table of probabilities? a. Joint probabilities b. Marginal probabilities c. Conditional probabilities d. None of the above

A

When a difference found in the results is larger than what we think is due to chance, what do we call the results? a. Statistically significant b. Statistically invalid c. Practically important d. None of the above

A

If r = -.7, what is the value of the coefficient of determination? a. -.49 b. .49 c. .70 d. -.70 e. None of these /not enough information to tell.

B

If you are predicting gas price using temperature, which is the X variable? a. Gas price b. Temperature c. Cannot tell without more information

B

Making comparisons, avoiding bias, and having enough data are the three criteria for what, according to our notes? a. A good survey b. A good experiment c. A good observational study d. Simpson's Paradox

B

OSU wanted to research how much money students spent on textbooks each semester. From a random sample of 200 students, they found that the average amount spent on textbooks for a semester is $300 and the distribution is skewed right. This indicates that: a. The median amount spent on textbooks would be greater than $300. b. The median amount spent on textbooks would be less than $300. c. The median amount spent on textbooks would be $300.

B

Residuals are found by taking a. Predicted - observed b. Observed - predicted

B

Suppose you give 10 people a taste test where they each try samples of two different brands of soda. You randomize the order in which the soda samples are given to the participants. After drinking both samples, they tell you which soda they liked best. What is a/the factor in this experiment? a. Number of participants b. Brand of soda c. The order in which the samples were given to the participants. d. Which soda the participant liked best.

B

The equation of a regression line is Y = 20 + 5X where X = hours studied and Y = exam score. Interpret the slope. a. As study time increases by 5 hours, exam score increases by 20 points. b. As study time increases by 1 hour exam score increases by 5 points. c. As exam score increases 1 point study time increases by 5 hours. d. None of the above.

B

The equation of a regression line is Y = 20 + 5X where X = hours studied and Y = exam score. Study time data ranged from 8 to 15 hours. Should we interpret the Y-intercept here? a. Yes. If someone studies 0 hours, they are expected to get 20 points. b. No. You should not interpret the Y-intercept in this situation. c. Not enough information to tell.

B

The variable that represents the outcome being measured in an experiment is called what? a. The independent variable b. The dependent variable c. The treatment d. The control

B

Undercoverage happens during what stage of the sampling process? a. When the sample is being selected. b. When the survey is designed. c. When the survey is implemented.

B

What does SSE stand for? a. Sum of Squares for Extrapolation. b. Sum of Squares for Error c. Sum of Statistics for Error d. None of the above

B

What does it mean for a sample to be truly random, according to our notes? a. Every individual in the sample has the same chance of being selected. b. Every group of the same size has the same chance of being selected. c. Everyone in the population has the same chance of being selected. d. None of the above.

B

What does it mean for a sample to be truly random, according to our notes? a. Every individual in the sample has the same chance of being selected. b. Every sample of the same size has the same chance of being selected. c. Every individual in the population has the same chance of being selected. d. None of the above.

B

What type of relationship does data with a correlation of -.3 have? a. Moderate downhill linear relationship b. Weak downhill linear relationship c. No linear relationship d. Cannot have a correlation of -.3.

B

What type of sample compares subgroups within the population? a. Simple random sample b. Stratified random sample c. Volunteer sample d. None of the above

B

Which measure of center splits the ordered data in half? a. The mean b. The median c. Both the mean and the median d. The IQR

B

Which measure of variability measures the concentration of the data around the mean? a. The IQR b. The standard deviation c. The correlation d. All of the above

B

Which measure of variability measures the concentration of the data around the mean? a. The IQR b. The standard deviation c. The correlation d. None of the above

B

Bob puts an ad in the school newspaper asking people to go to a certain website and take a survey. What type of sample will Bob get? a. A simple random sample. b. A cross-section sample. c. A self-selected sample. d. None of the above.

C

Going to the oval and asking OSU students for their opinion on tuition is what type of sample? a. Self-selected (volunteer) sample. b. Simple random sample c. Convenience sample d. Stratified random sample.

C

Suppose P(A) = .2, P(B) = .4 and P(A|B) = .3. Find P(A and B). a. .06 b. .08 c. .12 d. None of the above

C

Which of the following is (are) true? a. If A and B are independent, then P(A|B) = P(A|Bc) b. If P(A|B) = P(A|Bc), then A and B are independent. c. Both a) and b) are true d. Both a) and b) are false

C

Which of the following is the same as P(A or B)? a. P(A or B or both) b. P(At least one) c. All of the above

C

Which of the following statistics can NEVER be negative? a. Correlation b. Slope of the regression line c. Y-intercept of the regression line d. All of the above can be negative, if the data permits.

D