stat 1430 - homework/practice midterm/old tests for midterm

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false

If A and B are independent then P(A or B) becomes P(A)+P(B)-P(A)P(B).

mean < median

If a data set is skewed to the left, how will the mean and median compare? Correct!

points fall around the horizontal line Y = 0, random, no fan shapes

What should the residual plot look like if the regression line fits the data well?

The sign on the slope

When finding the correlation if you are given R-squared, you take the square root first. Then what do you look at to determine the sign for the correlation?

Whether gender of driver is related to the color being red (or not)

Which of the following questions can be answered by using a two-way table?

sample size, mean, SD

Which of the following summary measures cannot be directly calculated from a boxplot?

bayes

Which technique should you use when you have P(B|A) and some other probabilities but you are looking for P(A|B)?

box plot

Which type of graph is made from the 5-number summary?

SD

Which is more affected by skewness, the IQR or standard deviation?

SD

Which of the following can never be negative?

indep

If there is no relationship between two variables, then the

ye

P(A) = .20, P(B) = .30, P(A and B) = .06. Are A and B independent?

cant tell

Suppose 40% of the new employees at your company are males and 30% of the "old employees" are males. What percentage of ALL the employees are male?

no

Suppose 40% of the new employees at your company are males and 60% of the "old employees" are males. Are gender and type of employee (new/old) independent? Correct Answer

P(have disease | test positive)=.90

Suppose 90% of the patients who test positive for a disease actually have the disease. Write this as a probability.

false

Suppose the correlation between X and Y is .3. If you double all the X values and double all the Y values, the correlation between 2X and 2Y is .6.

false

Suppose the correlation between two variables X and Y is .8. That means the correlation between Y and X is -.8.

false

Suppose the correlation between yards rushing and yards passing is .6. That means the correlation between feet rushing and feet passing is .6 x 12 (since you multiply yards by 12 to convert to feet).

more than 9

Suppose you make 10 telemarketer calls. Which of the following is the complement of "at most" 9 sales?

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 standard deviation of this data set would also be measured in millions of dollars.

no, AND

The 4 cells of a two way table contain conditional probabilities.

SSE is equal to what?

The Sum of Squares for Error for any line going through the data.

moderate positive linear relationship

The correlation turns out to be .60

tru

You cannot see the mean on a boxplot.

two categorical

A two-way table allows us to examine the relationship between _____________________ variables.

random

All good samples are

true

An outlier in a data set can significantly affect the value of the mean but not the median

false

The sample size can be found by looking at the data in a boxplot.

falsw

The second level branches on a tree are marginal probabilities.

true

The wording of a survey question can affect the results

false

There can be different amounts of data in each section of a boxplot.

smallest

To find the best fitting line, you find the line with the ________ SSE.

true

Conditional probabilities are present on a tree.

false

Conditional probabilities can be found in the cells of a two-way table.

What type of variable was not accounted for in an experiment but affected the results?

Confounding variable

true

Correlation is affected by outliers.

no, no units

Correlation is in the same units as X and Y.

no, linear

Correlation measures the strength and direction of any relationship between X and Y.

16

Two randomly chosen customers are buying laundry soap at the store. 40% of the laundry soap on the shelves is Tide brand. What is the chance that both of them purchase Tide laundry soap?

flase

Undercoverage means you had alot of nonresponse in your sample.

A result due to more than chance

What is statistical significance?

Every sample of that same size has an equal chance of being selected.

What is the statistical definition of a random sample? Choose the best answer.

for disjoint

When is P(A or B) = P(A) + P(B)?

Mean of X, Mean of Y, SD of X, SD of Y, and r.

Which five descriptive statistics do you need to find the equation of the best fitting line?

boxplot

Which is best if you want to compare several data sets regarding shape, center, and variability?`

sd

Which measure of variability measures the concentration of the data around the mean?

boxplot

Which type of graph of quantitative data fits the following description: It shows skewed vs. symmetric shapes; it's easy to determine center and variability; it's good for skewed data sets; and it's easy to compare data sets:

false

You can compare two marginal distributions to see if the corresponding two variables are related.

no

You can never interpret the Y-intercept of the regression line.

nonresponse bias

You randomly choose 100 students from Stat 1350 to take a survey. 60 of them take the survey. What can occur with the other 40 people?

self-selected

You send out an email to all the students in Stat 1430 and you tell them to go to your website and do a survey. 100 students come forward. What kind of sample is this?

categorical

Your company operates in 4 regions and your boss numbers them 1, 2, 3 4. Is this variable quantitative or categorical?

Statistically significant

a difference in treatment is decided to be due to more than random chance

Extrapolation is what?

Plugging in X values outside the range of the data

same as data

SD units

As square feet increase by 1, selling price increases by $33.80

Selling price = $5,240 + $33.80 How do you interpret the slope for this equation?

has same as data

Standard deviation has no units.

true

Starting with the multiplication rule, you can show that P(B|A)=P(A and B)/P(A)

When a difference found in the results is larger than what we think is due to chance, what do we call the results?

Statistically significant

SSE

Sum of Squares for Error

12

Suppose 20% of OSU students are business majors, and of the business majors, 60% have internships over the summer. What percentage of OSU are business majors and have internships over the summer?

Conditional distribution of support (yes/no) given women

Suppose 35% of the women in a poll of Americans support candidate A for president (and 65% do not.) These results make up what kind of distribution?

true

Suppose 35% of the women in a poll support candidate A for president (and 65% do not.) In the same poll 45% of the men support candidate A for president (and 55% do not). Are gender and support (yes/no) related?

negative

Suppose the equation y = 3.45 - 2.58x represents a valid regression equation and X can be used to predict Y. From this information, we know that X and Y have _____________ correlation.

P(Female and Voting for A) = 0.30

Suppose the probability of someone being female and voting for Candidate A is 30%. What is the notation for this probability?

true

The median is not affected by outliers

he variable whose effects you want to study in an experiment is called the what?

factor

f you add the same value to every single number in a data set, the standard deviation also changes by that same value.

false

50th percentile, median, Q2

five number summary contains the min, max, Q1, Q3, and what other value

highest Q3

highest boxplot top

Which is better to use to see the most clear pattern in the d

histogram

Which statistic measures the distance between the middle 50% of the data? a.

iqr

symmetric box plot

median line in middle

False

median must be one of the numbers in the data set

What type of relationship does data with a correlation of -.5 have?

mod downhill linear

surve

most common observational study

Simpson's paradox always happens when you add a third variable to your two-way table.

no

What type of bias is minimized by making

repsonce

quantitatve

scatterplot

less on bottom, line lower on box

skew right

true

slices on a pie chart represent relative frequencies

0

standard deviation of the data set 1, 1, 1, 1

true

starting point can affect the way a graph looks

SD

the "average distance from the mean" is measured by the

In a histogram, the horizontal (X) axis is the variable you are measuring, and the vertical (Y) axis is the number or percenta

true

yea, is possible

two data sets with the same mean but different standard deviations

boxplot

type of graph is best for COMPARING two or more quantitative data sets, a boxplot or a histogram?

independent

x variable in an experiment

true

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

same

If you add the same positive number to every value of a data set what happens to the standard deviation?

temp

If you are predicting gas price using temperature, which is the X variable?

.12

P(A) = .3, P(B|A) = .4, P(B) = .5 What is P(A and B)?

.2

P(A) = .5, P(B) = .4 and P(A and B) = .1 What is P(B|A)?

false

The difference between an experiment and an observational study is an experiment randomly assigns subjects to treatments.

true

The difference between an experiment and an observational study is an experiment randomly assigns subjects to treatments.

the 5 numbers that are marked off on a boxplot

The five-number summary of a single data set of 100 numbers would be which of the following?

IQR is affected by outliers.

false

same

If you add 10 to every value of a data set, what happens to the standard deviation?

yes

A longer box in the boxplot means more variability in the data.

law of total probability

If you sum down the first column of values in this table to get .1 + .3 = .4, which statistical technique are you using behind the scenes?

Stratified Random Sample

If you want to ask the question: "How is the view from your seat?" where your population is the OSU's football stadium, what kind of sample should you use?

condition of patient

In the hospital example in your lecture notes, you found hospital A didn't do as well as hospital B when all the data was in one two-way table, but when an additional variable was examined, hospital A was better in all cases. What was that additional (confounding) variable that ended up reversing the results?

self-selected sample

What kind of sample occurs when you put an ad in the newspaper and ask readers to take your survey

BELOW

If a residual is negative, then that data point lies _________________ the regression line.

it's a weak positive linear relationship, do not proceed with a regression line

If the correlation is .2 what does that tell you about using a regression line to fit your data?

false

If the mean of a data set is large, the standard deviation has to be large also

.4

If the stock went up today, what is the chance it also went up yesterday? Choose the closest answer.

false

If there are a few very small values in a data set compared to the rest of the data, the mean will be larger than the median

false

If variables A and B are related in a certain way in a two way table (with 2 variables), no matter how many other variables you look at in addition to these two, the relationship will always stay the same.

1144

If you could choose four numbers from 1, 2, 3, 4 and repeated numbers were allowed (such as 1, 1, 3, 2), which set of four numbers would give you the largest standard deviation

false

If you have all the information filled in a two-way table, you can fill in all the information on a tree. But not the other way around

.4

P(A) = .2 and P(B) = .3. Suppose A and B are independent. What is P(A or B)?Choose the closest answer.

true

P(A) = P(A and B) + P(A and Bc) where Bc means "B complement"

The sum of the squared residuals equals SSE.

. How to the residuals relate to the SSE?

Residuals are found by taking

Observed - predicted

responce bias

3. When an individual in the sample responds but does not give the correct data, this is called:

75th

3rd, third

If you are predicting U.S. movie box office revenue by using Opening Weekend Revenue, which variable is X and which is Y

Opening Weekend Revenue is X and U.S. Box office revenue is Y.

marginal

A __________ distribution summarizes the information from one variable ONLY, without considering ANY information from another variable.

true

A bar graph using StatCrunch is a good way to visualize a marginal or a conditional distribution.

yes

A boxplot is a one-dimensional graph

false

A confidential survey is one in which they cannot link you to your data even if they wanted to.

false

A confidential survey is one in which they cannot link you to your data.

tru

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

moderate

A correlation of -.6 is considered to be what?

false

A flat histogram (with a line straight across) contains no variability whatsoever, according to our definition.

false

A flat histogram indicates no variability in the data.

distribution

A listing of all possible values in a data set and how often they occurred is called a data

tru

A listing of all the possible values of a data set and how often they occur is called a distribution.

False

A researcher is trying to use January temperatures to predict latitude. This means January temperature is the X (independent) variable and latitude is the Y (dependent) variable.

no

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. Are Bob and Bill independent in terms of being in the apartment?

false

Bob picks a name from the phone book using a random number generator, and then takes the first 100 names that come after that to make a sample. Is Bob's sample random?

bias from undercoverage

Bob wants to estimate the percentage of people who own a dog in his town, and he goes to all the apartment buildings to carry out his survey. He leaves out all the houses in the town. What kind of bias is this? Correct!

cant tell

Boxplot A and Boxplot B are drawn on the same axes. The box part of Boxplot A is shorter in length than the box part of Boxplot B. What can you tell about the two data sets?

What does it mean for a sample to be truly random, according to our notes?

Every sample of the same size has the same chance of being selected.

true

If 2 corresponding conditional distributions are different from each other in a two-way table, we know that the variables are related. Correct!

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?

false

In a boxplot you can tell the exact pattern of the data set (beyond just whether the data is skewed or symmetric.)

simpsons

In our lecture notes is an example involving two hospitals, A and B. If you compare patient outcomes for the hospitals, B is safer (has a lower death rate). But if you look only at the patients in poor condition, A is safer, and if you only look at the patients in good condition, A is safer. What is going on with this example?a. Bayes Rule

not indepedent

In the 2016 Presidential election, 63% of females voted and 59% of males voted. Does this mean that gender and voting are independent or not independent?

61

In the 2016 Presidential election, 63% of registered voting females actually voted and 59% of registered voting males actually voted. If research shows that 45% of registered voters are female and 55% of registered voters are male, what percentage of ALL registered voters actually voted in 2016?

good exp

Making comparisons, avoiding bias, and having enough data are the three criteria for what, according to our notes?

observation

Mike marks down the gas mileage of his two cars every time he fills them up with gas for 6 months straight. At the end he notes that his Mustang gets better mileage than his Corvette. Is this an experiment or an observational study?

Suppose you have events A and B. Which of the following is the same as the probability of at least one?

P(A or B)

If you are comparing two conditional distributions, (for example Opinion given Male compared to Opinion given Female), and the results are the same, what do you conclude?

a.Opinion and gender are independent. b

Which type of probabilities are in each of the 4 cells of a two-way table of probabilities?

and

Which of the following is (are) true?

If A and B are independent, then P(A|B) = P(A)

false

If the coefficient of determination is .81, the value of the correlation must be .9.

`tru

If the median is closer to Q1 than it is to Q3 then the data is skewed right. (lower line)


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