Stat 133 Recitation
Section 1.1
SOLUTIONS
1. Which of the following data sets is more spread around the mean, the first or the
second?
The second one because there are just as many smaller numbers as larger
numbers; the first graph has more numbers in the
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
education level. The output is given belo
Relations in Categorical Data
A statistics professor classifies his students according to their grade point average
(GPA) and their gender. The accompanying table gives the proportion of students
falling into the various categories. One student is selecte
1. The national proportion of adults who are concerned about nutrition is 0.35. You take a
random sample of 20 adults and count the number who are concerned about nutrition (call this
number X).
a. What is the mean of X?
Mean = np = 20 x .35 = 7 people
b.
1.
Inahistogram,theproportionofthetotalareawhichmustbetotheleftofthemedianis:
a. exactly0.50
b. lessthan0.50ifthedistributionisskewedtotheleft
c. morethan0.50ifthedistributionisskewedtotheright
d. between0.25and0.60ifthedistributionissymmetricandunimodal
Section5.1:ProbabilityRulesSOLUTIONS
1.
IfAandBaredisjointeventswithP(A)=0.70,thenP(B):
a. canbeanyvaluebetween0and1
b. canbeanyvaluebetween0and0.70
c. cannotbelargerthan0.30(remembertheyarenotnecessarilycomplements)
d. cannotbedeterminedwiththeinformatio
Section4.4:SamplingDistributionofaSampleMean
1.
TheCentralLimitTheoremstatesthat,ifarandomsampleofsize n isdrawnfroma
population,thenthesamplingdistributionofthesamplemean X :
a. isapproximatelynormalifn>30
b. isapproximatelynormalifn<30
c. isapproximatel
Section 5.4
Problem 1
The probability of flying on Airline A is 0.6. The probability of being on time given you fly on
Airline A is 0.8. The probability of being not on time given you dont fly on Airline A is 0.1.
Find the following probabilities:
Given:
Section 6.1: Confidence intervals for the sample mean
Note: All confidence intervals are 95% unless otherwise indicated. This also applies
on exams.
1. Suppose you want to estimate the average number of years employees have worked at
your company so far.
Stat 133 Recitation
Section 1.1
1. Which of the following data sets is more spread around the mean, the first or the
second?
30
Fr e que ncy
40
30
Fr e que ncy
40
20
20
10
10
0
20
40
60
80
0
100
20
40
60
80
100
2. We collected data OVER time and put it in
Section 1.3
1. Suppose Math exam scores have a normal dist with mean 70 and s = 10 and stat exam
scores have a normal dist with mean 80 and SD 5.
a. Draw a picture of the distribution of math scores. Draw a picture of the
distribution of stat exam scores.
2.1-2.2
Scatterplots and Correlation
1. A professor examines the relationship between minutes studying and exam score (out
of 200 points) for students in his course using data from 320 randomly selected students.
Use the results below to answer the follow
Section 4.3: Random Variables SOLUTIONS
1. Which of the following statements is always true? (If all are always true, select choice
d.)
a.
E(X+Y)=E(X)+E(Y)
b.
E(XY)=E(X)*E(Y)
c.
V(X+Y)=V(X)+V(Y)
d.
All of the above are always true.
2.
V(-3)= _.
a. -3
b. 9
Samples, Surveys, and Experiments
1.
Which of the following sampling plans uses some form of random selection? (Choose
all that apply)
a. Simple random sampling.
b. Stratified random sampling.
c. Self-selected (volunteer) sample
2.
A pharmaceutical compan
2.1-2.2
Scatterplots and Correlation-SOLUTIONS
1. A professor examines the relationship between minutes studying and exam score (out
of 200 points) for students in his course using data from 320 randomly selected students.
Use the results below to answer
Section2.5
RelationsinCategoricalData
14. A statistics professor classifies his students according to their grade point average
(GPA)andtheirgender.Theaccompanyingtablegivestheproportionofstudents
fallingintothevariouscategories.Onestudentisselectedatra
Samples, Surveys, and Experiments
1.
Which of the following sampling plans uses some form of random selection? (Choose
all that apply)
a. Simple random sampling.
b. Stratified random sampling.
c. Self-selected (volunteer) sample
2.
A pharmaceutical compan
1. Which of the following statements is always true? (If all are always true, select d)
a.
X+Y = X + Y
b.
XY = X * Y
c.
2X+Y = 2X + 2Y
d.
All of the above are always true.
2.
Suppose X is always -3. Then 2X = _.
a. -3
b. 9
c. 0
d. Not possible
3.
If Corr
Section4.4:SamplingDistributionofXbar( X )
1.
TheCentralLimitTheoremstatesthat,ifarandomsampleofsize n isdrawnfroma
population,thenthesamplingdistributionofthesamplemean X :
a. isapproximatelynormalifn>30
b. isapproximatelynormalifn<30
c. isapproximatelyn
Section5.1:ProbabilityRules
1.
IfAandBaredisjointeventswithP(A)=0.70,thenP(B):
a. canbeanyvaluebetween0and1
b. canbeanyvaluebetween0and0.70
c. cannotbelargerthan0.30
d. cannotbedeterminedwiththeinformationgiven
2.
IfP(A)=0.65,P(B)=0.58,andP(AandB)=0.76,th
Section 5.2: Binomial Distribution
1. The national proportion of adults who are concerned about nutrition is 0.35. You take a
random sample of 20 adults and count the number who are concerned about nutrition
(call this number X).
a. What is the mean of X?
Section 5.4
Problem 1
The probability of flying on Airline A is 0.6. The probability of being on time given you
fly on Airline A is 0.8. The probability of being not on time given you dont fly on
Airline A is 0.1. Find the following probabilities:
a.
b.
c
Section 6.1: Confidence intervals for the sample mean
Note: All confidence intervals are 95% unless otherwise indicated. This also applies
on exams.
1. Suppose you want to estimate the average number of years employees have worked at
your company so far.
Recitation Probability Practice Problems
(Show all your work to get credit - work means symbols not just
numbers!)
1. Do primate parents treat female and male children differently? Data were collected from 39
groups of three, one adult female(mother), one
SOLUTIONS
1.
Inahistogram,theproportionofthetotalareawhichmustbetotheleftofthemedianis:
a. exactly0.50
b. lessthan0.50ifthedistributionisskewedtotheleft
c. morethan0.50ifthedistributionisskewedtotheright
d. between0.25and0.60ifthedistributionissymmetrican
Section 1.3: Normal Distribution
1. Suppose Math exam scores have a normal dist with mean 70 and s = 10 and stat
exam scores have a normal dist with mean 80 and SD 5.
a. Draw a picture of the distribution of math scores. Draw a picture of the
distribution
Regression (Part 1)
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 education level. The output is given below.
Descripti