Stat1430
Recitation7Solutions
Sections2.32.4part2
Checkingthefitofaregressionline:
A. r2isthe
ofthe
in
thatis
bytheits
relationshipwithX.
B. r2isalwaysbetweenwhichtwovalues?
Example:
DescriptiveStatistics:Education,Internet
Variable
Mean StDev
Variance
Stat 1430
Recitation 5B
Section 2.5: Relations in Categorical Data
SOLUTIONS
1. 722 randomly selected students in a business school were asked what their major was. Half the students were
males and half were females.
Distribution of Major for Males
35%
5%
4bSTAT 1430
REC 4B SOLUTONS
SEC 2.1-2.4
REGRESSION
1. Why is Total U.S. Box Office Revenue considered the Y (dependent) variable in this
case?
Total U.S. Box Office Revenue is the one that is being predicted.
2. We need to find a good X (independent) vari
STAT 1430
Sec 2.1-2.2
REC 4A SOLUTIONS
Scatterplots & Correlation
Basics of correlation:
1. Scatterplots examine relationships between what type(s) of variables?
a) Categorical
b) Quantitative
c) Both categorical and quantitative variables
2. Correlation
Stat 1430
Extra Practice Problems
Correlation and Regression
1. Write down a data set that contains five (x, y) points whose correlation is EXATLY
one. Draw a scatterplot of your data set below. (answers may vary here)
Data
Point
X
value
Y
value
1
2
3
4
5
Stat 1430
Recitation 7B SOLUTIONS
Probability Review
Bob thinks more female college students eat breakfast in the morning than males.
Suppose a survey of college students asked whether they ate breakfast this morning or not, along
with their gender. The r
Stat 1430
Recitation 7B
2.5, 5.1, 5.2 Review
Bob thinks more female college students eat breakfast in the morning than males.
Suppose a survey of college students asked whether they ate breakfast this morning or not, along
with their gender. The results a
Stat 1430
Rec 3B
Boxplots
Use the graphic below to answer the problems 1-3: The number of robberies each year
was recorded for each of two banks over a 20-year period. The boxplots are shown below.
7
6
Robberies
5
4
3
2
1
A
B
1.
The amount of variability
STAT 1430
Recitation 3A
1.1, 1.2: Excel for Desc Stats
Data Set: Billionaires in the world as published by fortune magazine in 1992
Variables:
Wealth: Wealth of family or individual in billions of dollars
Age: Age in years (for families it is the maximu
STAT 1430
Recitation 2B
Section 1.1 1.2
MC/TF
1. In general, can you recreate the original data values from its histogram?
a. Yes
b. No
2. We know that if a histogram is skewed left, then the mean is less than the median.
WHY?
a. There are a few small val
Stat 1430 Recitation 2A
SEC 3.2
EXPERIMENTS
Suppose we want to study and compare the volume of popcorn produced by two brands of
microwave popcorn. We will take 30 bags of popcorn of brand A and 30 of brand B and cook
them various amounts of time in a ran
STAT 1430 Recitation 7A
5.2 conditional probability
Names_
GROUP #_
Use the information below to answer #1-#7
28% of Fortune 500 companies are laying off employees. Moreover, 18% of those laying off employees are
cutting down on advertising expenses. Of t
Stat 133 Recitation Solutions
2.3 and 2.4
Regression (Part 1) (SOLUTIONS)
We are comparing years of education and hours on the internet in the last month, to see
if a relationship exists. If a relationship does exist, we want to predict Internet use using
Stat 1430
SOLUTIONS
Recitation 6B
Section 5.1 Problems: Probability Rules Part 2
1. The following table shows data from a random sample of 100 drivers
who own cars. Number of speeding tickets in the last 6 months, and
whether or not they drive a fast car
STAT 1430
REC 9B (SOLUTIONS)
SEC 4.3
CONTINUOUS R.V.
For every question in this recitation assignment, assume X is a continuous random variable
with a probability density function). Draw pictures where appropriate and helpful.
1. Which of the following ca
STAT 1430
REC 10A (SOLUTIONS)
SEC 4.3
CONTINUOUS R.V.
1. A fast food manager wants to be prepared to have enough of COIN
change (pennies, nickels, dimes, and quarters) at the drive through
window ready to give to customers. Let X be the amount of COIN
cha
STAT 1430
REC 9A (SOLUTIONS)
SEC 4.3
DISCRETE R.V.
Instructions:
For full credit, use proper notation and write out any formulas you use during this
recitation (when applicable). Answers without supporting work will not be given full
credit.
Multiple Choi
Install the Data Analysis ToolPak
Using Excel 2007/ 2010
1. Open an Excel worksheet.
2. Click on
Tab.
3. Look under the Analysis group; if there is not a choice that says
you need to install the Data Analysis ToolPak.
4. For Excel 2007 only: Click the Mic
Install the Data Analysis ToolPak
Using Excel 2007
1. Open an Excel worksheet.
2. Click on
Tab.
3. Look under the Analysis group; if there is not a choice that says
you need to install the Data Analysis ToolPak.
4. Click the Microsoft Office Button
, and
STAT 1430
Recitation 3B SOLUTIONS
SD and Boxplots
STANDARD DEVIATION
1. Suppose the mean of a data set is 10, the median is 20, and the standard deviation is 5.
What happens if you multiply all the values in the data set by -1?
a. The mean, median, and SD
Binomial Distribution
Binomial distribution
Type of variable: Discrete: x=0,1,2,.n (sample size)
Used when: counting # of times a certain event occurs
in the sample
Example: # who are in favor, # of women
KNOW THESE WELL
Conditions for a binomial
1. Yo
Normal Distribution
The Normal Distribution
Type of variable: continuous
Shape bell-curve, symmetric around mean
Center mean mu
Spread (variability) sigma= standard deviation
Picture
sigma
mu
68-95-99.7 Rule: rough idea of normal
probabilities
1) Abou
Data Collection: Samples and
Surveys
Methods of Collecting Data
Observational Studies (part 1)
Most common observational study: Surveys
Experiments (part 2)
The difference between the two:
-observational study- the experimenter has no influence, they