A professor has kept records on grades that students have earned in his class. If he wants to examine the % of students earning the grades A, B, C, D, and F during the most recent term, which kind of plot would he make?

2 sections of a class took the same quiz. Section A has 15 students who had a mean score of 80, and Section B had 20 students with a mean score of 90. Overall, what was the approximate mean score for all of the students on the quiz?

Suppose that a normal model described student scores in a history class. Parker has a standardized score (z-score) of +2.5. This means that Parker:

Your Stats teacher tells you that your test score was in the 3rd quartile for the class. Which is true?

I) You got 75% on the test

II) You can't really tell what this means without knowing the standard deviation

III) You can't really tell what this means unless the class distribution is nearly normal

The advantage of making a stem and leaf display instead of a dotplot is that a stem and leaf display:

The 5 number summary of credit hours for 24 students in a statistics class is:
Min:13
Q1:15
Median: 16.5
Q3: 18
Max: 22
From the info we know:

Which of the followinf data summaries are changed by adding a constant to each data value?

I) the mean

II) the median

III) the standard deviation

If we want to discuss gaps and clusters in a data set, which of the following should NOT be chosen to display the data set?

All BUT one of these statements contain a mistake. Which one is true?

Which statement about influential points is true?

I) removal of an influential point changes the regression line

II) data points that are outliers in the horizontal direction are more likely to be influential points than points that are outliers in the vertical direction

III) influential points have large residuals

Residuals are:

Which is true?

I) random scatter in the residuals indicates a model with high predictive power

II) if 2 variables are very strongly associated, then the correlation between them will be near +1 or -1

III) the higher the correlation between 2 variables the more likely the association is based on cause and effect

A company's sales increase by the same amount each year. This growth is:

It's easy to measure the circumference of a tree's trunk, but not so to measure its height. Foresters developed a model for ponderosa pines that they use to predict the tree;s height (in feet) from the circumference of its trunk (in inches):  $$\ln h\wedge=-1.2+1.4\left(\ln C\right)$$  A lumberjack finds a tree with a circumference of 60"; how tall does this model estimate the tree to be?

2 variables that are actually NOT related to each other may nonetheless have a very high correlation because they both result from some other, possibly hidden, factor. This is an example of:

A correlation of 0 between 2 quantitative variables means that:

A residual plot is useful because:

I) it will help us see whether our model was appropriate

II) it might show a pattern in the data that was hard to see in the original scatterplot

III) it will clearly identify the influential points

Which of the following is NOT a goal of re-expressing data?

The correlation coefficient between the hours that a person is awake during a 24 hr period and the hours that same person is asleep during a 24 hr period is most likely to be:

$$\ \$$  A regression analysis of students' college GPAs and their high school GPAs found  $$R^2=.311$$  . Which of these is true?
I) high school GPA accounts for 31.1% of college GPA
II) 31.1% of college GPAs can be correctly predicted with this model
III) 31.1% of the variance in college GPA can be accounted for by this model

When using midterm exam scores to predict a student's final grade in the class. the student would prefer to have a:

A company sponsoring a new internet search engine wants to collect data on the ease of using it, Which is the best way to collect the data?

More dogs are being diagnosed with thyroid problems than have been diagnosed in the past. A researcher identifies 50 puppies without thyroid problems and kept records of their diets fro several years to see if any developed thyroid problems. This is a(n):

A chemistry professor who teaches a large lecture class surveys his students who attend his class about how hw can make the class more interesting hoping he can get more students to attend. This survey method suffers from:

Double-blinding in experiments is important so that...

I) the evaluators do not know which treatment group the participants are in

II) the participants don;t know which treatment group they're in

III) no one knows which treatment any of the participants are getting

Placebos are a tool for:

Which of the following is NOT required in an experimental design?

Which statement about bias is true?

I) bias results from random variation and will always be present

II) bias results from a sampling method likely to produce samples that do not represent the population

III) bias is usually reduced when sample size is bigger

In an experiment the primary purpose of blinding is to reduce:

A bicycle shop equips 60% if their bikes with a water bottle holder, 55% of the bikes they sell have a kickstand attached to the bike, 34% of the bikes sold have both features. What is the probability that a randomly selected bicycle will have a kickstand OR a water bottle holder?

6 republicans and 4 democrats have applied for 2 open positions on a planning committee. Since all the applicants are qualified to serve, the City Council decides to pick the 2 new members randomly. What is the probability that BOTH come from the SAME party?

Political analysts estimate the probability that Hillary Clinton will run for president in 2020 is 45%, and the probability that NY's Governor George Pataki will run is 20%. If their political decisions are independent, what is the probability that ONLY Hillary runs for president?

Some marathons allow 2 runners to "split: the marathon by each running a half marathon. Alice and Sharon plan to split a marathon. Alice's half marathon times average 92 mins with a st. dev. of 4 mins., and Sharon's half marathon times average 96 mins with a st. dev. of 2 mins. The expected time for Alica and Sharon to complete a full marathon is 92+96=188 mins. What is the st. dev. of their total time?