Key

The 1st Hourly

Math 1107

Summer Term 2008

 

Protocol

 

You will use only the following resources: Your individual calculator; individual tool-sheet (single 8.5 by 11 inch sheet); your writing utensils; blank paper (provided by me) and this copy of the hourly. Do not share these resources with anyone else.

 

In each case, show complete detail and work for full credit. Follow case study solutions and sample hourly keys in presenting your solutions. Work all six cases. Using only one side of the blank sheets provided, present your work. Do not write on both sides of the sheets provided, and present your work only on these sheets. All of your work goes on one side each of the blank sheets provided. Space out your work. Do not share information with any other students during this hourly.

 

Show all work and full detail for full credit. Provide complete discussion for full credit.

 

Sign and Acknowledge:

 

I agree to follow this protocol.

 

______________________________________________________________________________________

Name (PRINTED)                                       Signature                                         Date

 

Case One | Triplet of Dice |Random Variable

We have a triplet of dice – a fair d2 {faces 1, 2}, a fair d3 {faces 1, 2, 3} and a loaded d4 {faces 0, 1, 2, 3} – note the probability model for the d4 below. 

 Face

Probability

0

0.40

1

0.25

2

0.25

3

0.10

Total

1.00

We assume that the dice operate separately and independently of each other. Suppose that our experiment consists of tossing the dice, and noting the resulting face-triplet.

1. List the possible triplets of face values, and compute a probability for each triplet of face values.

 

Write the triplets as (d2,d3,d4). There are 2*3*4=24 triplets.

 

Pr{(1,1,0)} = Pr{1 from d2}*Pr{1 from d3}*Pr{0 from d4} = (1/2)*(1/3)*(4/10) = 4/60 = 16/240

Pr{(1,2,0)} = Pr{1 from d2}*Pr{2 from d3}*Pr{0 from d4} = (1/2)*(1/3)*(4/10) = 4/60 = 16/240

Pr{(1,3,0)} = Pr{1 from d2}*Pr{3 from d3}*Pr{0 from d4} = (1/2)*(1/3)*(4/10) = 4/60 = 16/240

Pr{(2,1,0)} = Pr{2 from d2}*Pr{1 from d3}*Pr{0 from d4} = (1/2)*(1/3)*(4/10) = 4/60 = 16/240

Pr{(2,2,0)} = Pr{2 from d2}*Pr{2 from d3}*Pr{0 from d4} = (1/2)*(1/3)*(4/10) = 4/60 = 16/240

Pr{(2,3,0)} = Pr{2 from d2}*Pr{3 from d3}*Pr{0 from d4} = (1/2)*(1/3)*(4/10) = 4/60 = 16/240

 

Pr{(1,1,1)} = Pr{1 from d2}*Pr{1 from d3}*Pr{1 from d4} = (1/2)*(1/3)*(1/4) = 1/24 = 10/240

Pr{(1,2,1)} = Pr{1 from d2}*Pr{2 from d3}*Pr{1 from d4} = (1/2)*(1/3)*(1/4) = 1/24 = 10/240

Pr{(1,3,1)} = Pr{1 from d2}*Pr{3 from d3}*Pr{1 from d4} = (1/2)*(1/3)*(1/4) = 1/24 = 10/240

Pr{(2,1,1)} = Pr{2 from d2}*Pr{1 from d3}*Pr{1 from d4} = (1/2)*(1/3)*(1/4) = 1/24 = 10/240

Pr{(2,2,1)} = Pr{2 from d2}*Pr{2 from d3}*Pr{1 from d4} = (1/2)*(1/3)*(1/4) = 1/24 = 10/240

Pr{(2,3,1)} = Pr{2 from d2}*Pr{3 from d3}*Pr{1 from d4} = (1/2)*(1/3)*(1/4) = 1/24 = 10/240

 

Pr{(1,1,2)} = Pr{1 from d2}*Pr{1 from d3}*Pr{2 from d4} = (1/2)*(1/3)*(1/4) = 1/24 = 10/240

Pr{(1,2,2)} = Pr{1 from d2}*Pr{2 from d3}*Pr{2 from d4} = (1/2)*(1/3)*(1/4) = 1/24 = 10/240

Pr{(1,3,2)} = Pr{1 from d2}*Pr{3 from d3}*Pr{2 from d4} = (1/2)*(1/3)*(1/4) = 1/24 = 10/240

Pr{(2,1,2)} = Pr{2 from d2}*Pr{1 from d3}*Pr{2 from d4} = (1/2)*(1/3)*(1/4) = 1/24 = 10/240

Pr{(2,2,2)} = Pr{2 from d2}*Pr{2 from d3}*Pr{2 from d4} = (1/2)*(1/3)*(1/4) = 1/24 = 10/240

Pr{(2,3,2)} = Pr{2 from d2}*Pr{3 from d3}*Pr{2 from d4} = (1/2)*(1/3)*(1/4) = 1/24 = 10/240

 

Pr{(1,1,3)} = Pr{1 from d2}*Pr{1 from d3}*Pr{3 from d4} = (1/2)*(1/3)*(1/10) = 1/60 = 4/240

Pr{(1,2,3)} = Pr{1 from d2}*Pr{2 from d3}*Pr{3 from d4} = (1/2)*(1/3)*(1/10) = 1/60 = 4/240

Pr{(1,3,3)} = Pr{1 from d2}*Pr{3 from d3}*Pr{3 from d4} = (1/2)*(1/3)*(1/10) = 1/60 = 4/240

Pr{(2,1,3)} = Pr{2 from d2}*Pr{1 from d3}*Pr{3 from d4} = (1/2)*(1/3)*(1/10) = 1/60 = 4/240

Pr{(2,2,3)} = Pr{2 from d2}*Pr{2 from d3}*Pr{3 from d4} = (1/2)*(1/3)*(1/10) = 1/60 = 4/240

Pr{(2,3,3)} = Pr{2 from d2}*Pr{3 from d3}*Pr{3 from d4} = (1/2)*(1/3)*(1/10) = 1/60 = 4/240

 

2. Define SUM as the sum of the face values in the triplet. Compute and list the possible values for the variable SUM, and compute a probability for each value of SUM.

 

SUM[(1,1,0)}] = 1+1+0 = 2

SUM[(1,2,0)}] = 1+2+0 = 3

SUM[(1,3,0)}] = 1+3+0 = 4

SUM[(2,1,0)}] = 2+1+0 = 3

SUM[(2,2,0)}] = 2+2+0 = 4

SUM[(2,3,0)}] = 2+3+0 = 5

 

SUM[(1,1,1)}] = 1+1+1 = 3

SUM[(1,2,1)}] = 1+2+1 = 4

SUM[(1,3,1)}] = 1+3+1 = 5

SUM[(2,1,1)}] = 2+1+1 = 4

SUM[(2,2,1)}] = 2+2+1 = 5

SUM[(2,3,1)}] = 2+3+1 = 6

 

SUM[(1,1,2)}] = 1+1+2 = 4

SUM[(1,2,2)}] = 1+2+2 = 5

SUM[(1,3,2)}] = 1+3+2 = 6

SUM[(2,1,2)}] = 2+1+2 = 5

SUM[(2,2,2)}] = 2+2+2 = 6

SUM[(2,3,2)}] = 2+3+2 = 7

 

SUM[(1,1,3)}] = 1+1+3 = 5

SUM[(1,2,3)}] = 1+2+3 = 6

SUM[(1,3,3)}] = 1+3+3 = 7

SUM[(2,1,3)}] = 2+1+3 = 6

SUM[(2,2,3)}] = 2+2+3 = 7

SUM[(2,3,3)}] = 2+3+3 = 8

 

Pr{SUM=2} = Pr{(1,1,0)} = 16/240

 

Pr{SUM=3} = Pr{One of  (1,2,0), (2,1,0), (1,1,1) Shows} = Pr{(1,2,0)}+ Pr{(2,1,0)}+ Pr{(1,1,1)} = (16/240)+(16/240)+(10/240) = 42/240

 

Pr{SUM=4} = Pr{One of (1,3,0), (2,2,0) , (1,2,1), (2,1,1), (1,1,2)  Shows} = Pr{(1,3,0)}+Pr{(2,2,0)}+Pr{(1,2,1)}+Pr{(2,1,1)}+Pr{(1,1,2)} = (16/240)+(16/240)+(10/240)+(10/240)+(10/240) = 62/240

 

Pr{SUM=5} = Pr{One of (2,3,0), (1,3,1), (2,2,1), (1,2,2), (2,1,2), (1,1,3) Shows} = Pr{(2,3,0)}+Pr{(1,3,1)}+Pr{(2,2,1)}+Pr{(1,2,2)}+Pr{(2,1,2)} + Pr{(1,1,3))= (16/240)+(10/240)+ (10/240)+ (10/240)+ (10/240) + (4/240) = 60/240

 

Pr{SUM=6} = Pr{One of (2,3,1), (1,3,2), (2,2,2), (1,2,3), (2,1,3) Shows} = Pr{(2,3,1)}+Pr{(1,3,2)}+Pr{(2,2,2)}+ Pr{(1,2,3)}+Pr{(2,1,3)} = (10/240)+ (10/240)+ (10/240)+(4/240)+(4/240) = 38/240

 

Pr{SUM=7} = Pr{One of (2,3,2), (1,3,3), (2,2,3) Shows} = Pr{(2,3,2)}+ Pr{(1,3,3)}+Pr{(2,2,3)} = (10/240)+(4/240) +(4/240) = 18/240

 

Pr{SUM=8} = Pr{(2,3,3)} = 4/240

 

Case Two | Long Run Argument and Perfect Samples | Plurality in US Resident Pregnancies

 

Plurality is the number of siblings born as the result of a single pregnancy. Singleton pregnancies yield one born infant, twin pregnancies yield two infants and triplet pregnancies yield three infants. Suppose that the probabilities tabled below apply to pregnancies to US resident mothers with pregnancies yielding one or more live births:

 

Plurality

Probability

Singleton (1)

0.9660

Twins (2)

0.0330

Triplets+ (3 or more)

0.0010

Total

1.00

 

1. Interpret each probability using the Long Run Argument.  

 

In long runs of sampling with replacement, approximately 96.6% of US resident pregnancies yielding one or more live births are a singleton pregnancies.

In long runs of sampling with replacement, approximately 3.3% of US resident pregnancies yielding one or more live births are twin pregnancies.

In long runs of sampling with replacement, approximately 0.1% of US resident pregnancies yielding one or more live births are triplet or more pregnancies.

 

 

2. Compute and discuss Perfect Samples for n=2500.

 

Esingleton = n*Psingleton = 2500*0.9660 = 2415

Etwin = n*Ptwin = 2500*0.033 = 82.5

Etriplet+ = n*Ptriplet+ = 2500*0.001 = 2.5

 

In random samples of 2500 US resident pregnancies yielding one or more live births, approximately 2415 sampled pregnancies are singleton pregnancies.

In random samples of 2500 US resident pregnancies yielding one or more live births, approximately 82.5 sampled pregnancies are twin pregnancies.

In random samples of 2500 US resident pregnancies yielding one or more live births, approximately 2.5 sampled pregnancies are triplet or more pregnancies.

 

Case Three | Color Slot Machine | Conditional Probabilities

 

Here is our slot machine – on each trial, it produces a 10-color sequence, using the table below:

 

Sequence*

Probability

RRBBRRYRRR

.10

RRGGRGBRRB

.10

BBYYGGYGBR

.15

GRRGGYBRGG

.10

BGYGYRYGYY

.25

RRYYGRRBBY

.10

YYGBYYBGRR

.20

Total

1.00

*B-Blue, G-Green, R-Red, Y-Yellow, Sequence is numbered from left to right: (1st 2nd 3rd 4th 5th6th7th 8th 9th 10th )

Compute the following conditional probabilities:

 

Pr{ Yellow Shows Exactly Twice | Blue Shows}

 

 

Sequence*

Probability

RRBBRRYRRR

.10

RRGGRGBRRB

.10

BBYYGGYGBR

.15

GRRGGYBRGG

.10

BGYGYRYGYY

.25

RRYYGRRBBY

.10

YYGBYYBGRR

.20

Total

1.00

 

Pr{Blue Shows} = Pr{One of RRBBRRYRRR, RRGGRGBRRB, BBYYGGYGBR, GRRGGYBRGG, BGYGYRYGYY, RRYYGRRBBY, YYGBYYBGRR Shows} =

Pr{RRBBRRYRRR} + Pr{RRGGRGBRRB} + Pr{BBYYGGYGBR} + Pr{GRRGGYBRGG} + Pr{BGYGYRYGYY} + Pr{RRYYGRRBBY} + Pr{YYGBYYBGRR} = .1+.1+.15+.1+.25+.1+.2 = 1.00

 

Sequence*

Probability

 

 

Total

0

 

 

Pr{ Yellow Shows Exactly Twice and  Blue Shows} = 0

 

 

Pr{ Yellow Shows Exactly Twice | Blue Shows} = Pr{ Yellow Shows Exactly Twice and Blue Shows}/Pr{Blue Shows} = 0/1 =0

 

Pr{ Green Shows | “BR” Shows }

 

Sequence*

Probability

RRBBRRYRRR

.10

RRGGRGBRRB

.10

BBYYGGYGBR

.15

GRRGGYBRGG

.10

Total

.45

 

Pr{ “BR” Shows } = Pr{One of RRBBRRYRRR, RRGGRGBRRB, BBYYGGYGBR, GRRGGYBRGG Shows} = Pr{RRBBRRYRRR}+ Pr{ RRGGRGBRRB}+

Pr{BBYYGGYGBR}+ Pr{GRRGGYBRGG} = .1+.1+.15+.1 = .45

 

 

Pr{Green Shows and “BR” Shows}

 

Sequence*

Probability

RRGGRGBRRB

.10

BBYYGGYGBR

.15

GRRGGYBRGG

.10

Total

.35

 

Pr{ Green Shows and “BR” Shows } = Pr{One of RRGGRGBRRB, BBYYGGYGBR, GRRGGYBRGG Shows} = Pr{ RRGGRGBRRB}+

Pr{BBYYGGYGBR}+ Pr{GRRGGYBRGG} =.1+.15+.1 = .35

 

Pr{ Green Shows | “BR” Shows } = Pr{ Green Shows and “BR” Shows }/Pr{ “BR” Shows } = .35/.45 = 7/9

 

 

Pr{ Red Shows | Green Shows}

 

Sequence*

Probability

RRGGRGBRRB

.10

BBYYGGYGBR

.15

GRRGGYBRGG

.10

BGYGYRYGYY

.25

RRYYGRRBBY

.10

YYGBYYBGRR

.20

Total

.90

 

Pr{Green Shows} = Pr{One of RRGGRGBRRB, BBYYGGYGBR, GRRGGYBRGG, BGYGYRYGYY, RRYYGRRBBY, YYGBYYBGRR Shows} =

Pr{RRBBRRYRRR} + Pr{RRGGRGBRRB} + Pr{BBYYGGYGBR} + Pr{GRRGGYBRGG} + Pr{BGYGYRYGYY} + Pr{RRYYGRRBBY} + Pr{YYGBYYBGRR} = .1+.15+.1+.25+.1+.2 = .90

 

Pr{ Red Shows and Green Shows}

 

Sequence*

Probability

RRGGRGBRRB

.10

BBYYGGYGBR

.15

GRRGGYBRGG

.10

BGYGYRYGYY

.25

RRYYGRRBBY

.10

YYGBYYBGRR

.20

Total

.90

 

Pr{ Red and Green Show } = Pr{One of RRGGRGBRRB, BBYYGGYGBR, GRRGGYBRGG, BGYGYRYGYY, RRYYGRRBBY, YYGBYYBGRR Shows} =

Pr{RRBBRRYRRR} + Pr{RRGGRGBRRB} + Pr{BBYYGGYGBR} + Pr{GRRGGYBRGG} + Pr{BGYGYRYGYY} + Pr{RRYYGRRBBY} + Pr{YYGBYYBGRR} = .1+.15+.1+.25+.1+.2 = .90

 

Pr{ Red Shows | Green Shows} = Pr{ Red Shows and Green Shows}/Pr{ Green Shows} = .9/.9 = 1

 

 

Case Four | Color Slot Machine | Probability Rules

 

Using the color slot machine from case three, compute the following probabilities. If a rule is specified, you must use that rule.

 

1. Pr{“YR” Shows }

 

Sequence*

Probability

RRBBRRYRRR

.10

BGYGYRYGYY

.25

Total

.35

 

Pr{Blue Shows} = Pr{One of RRBBRRYRRR, BGYGYRYGYY Shows} =

Pr{RRBBRRYRRR} + Pr{BGYGYRYGYY} = .1+.25 = .35

 

2. Pr{ Green Shows 2nd or 3rd }

 

Sequence*

Probability

RRGGRGBRRB

.10

BGYGYRYGYY

.25

YYGBYYBGRR

.20

Total

.55

 

Pr{{ Green Shows 2nd or 3rd } = Pr{One of RRGGRGBRRB, BGYGYRYGYY, YYGBYYBGRR Shows} =

Pr{RRGGRGBRRB} + Pr{BGYGYRYGYY} + Pr{YYGBYYBGRR} = .1+.25+.1+.2 = .55

 

 

 

3. Pr{ Green Shows } – Use the Complementary Rule

 

 

 

Sequence*

Probability

RRBBRRYRRR

.10

Total

.10

 

Pr{No Green Shows} = Pr{RRBBRRYRRR} = .10

Pr{Green Shows } = 1 – Pr{No Green Shows } = 1 –.1 = .90

 

Optional Check

 

Sequence*

Probability

RRGGRGBRRB

.10

BBYYGGYGBR

.15

GRRGGYBRGG

.10

BGYGYRYGYY

.25

RRYYGRRBBY

.10

YYGBYYBGRR

.20

Total

.90

 

Pr{Blue Shows} = Pr{One of RRGGRGBRRB, BBYYGGYGBR, GRRGGYBRGG, BGYGYRYGYY, RRYYGRRBBY, YYGBYYBGRR Shows} =

Pr{RRGGRGBRRB} + Pr{BBYYGGYGBR} + Pr{GRRGGYBRGG} + Pr{BGYGYRYGYY} + Pr{RRYYGRRBBY} + Pr{YYGBYYBGRR} =.1+.15+.1+.25+.1+.2 = .90

 

Case Five | Design Fault Spot

 

In each of the following a brief description of a design is presented. Briefly identify faults present in the design. Use the information provided. Be brief and complete.

 

1. A sample of college students is needed for a sample survey. The people running the study decide on the following: they divide the population of colleges and universities into groups based upon enrollment size and whether the college or university is private or public; next, they used judgment to select one school from each group. Then, a random sample of students was selected from each selected school.

 

The first stage of sampling is not random – every stage of sampling should be random.

2. In a comparative clinical trial, treatment methods are compared in the treatment of Condition Z, which when left untreated leads to severe complications and possibly death. Suppose we have a new candidate treatment, and further suppose that a standard treatment for a similar (but different) disease is available. A comparative clinical trial is proposed that would compare these treatments in patients with condition Z.

The “standard” treatment isn’t standard for Condition Z. 

3. A sample survey design employs a random sample of the United Kingdom (England, Wales, Scotland, and Northern Ireland) adult subjects (18 years or older, non-institutionalized). The research objective of the survey is to determine attitudes of Irish* subjects regarding Birth Control. Assume that the Survey Instrument is written properly and delivered in an unbiased way.

 * Ireland is split into two countries: Northern Ireland and Ireland

 

The sampling includes non-Irish subjects, and excludes Irish subjects in N. Ireland.

 

4. A survey design targets a nation-wide (US) population of Public High School biology teachers by mailing survey instruments to a random sample of these teachers. Assume that there are no problems with the wording of the survey instrument. A total of 200 (out of 20,000 mailed) surveys are returned. Among other things, an analysis of the 200 responses indicated that 19% of the respondents thought that "dinosaurs and humans lived at the same time.." The researchers claim that their results and sample reliably reflect the nation-wide population of HS Biology Teachers.

 

The sampling excludes private high schools, and the response rate is too low.


Case Six | Clinical Trial Sketch | Study of Tamoxifen and Raloxifene (STAR) for the Prevention of Breast Cancer

 

The purpose of this study is to examine the performance of the drug Raloxifene (relative to the drug Tamoxifen) in reducing the incidence of breast cancer in postmenopausal women1 who are at increased risk of the disease2.

 

1. Postmenopausal women at increased risk for developing invasive breast cancer, who meet one of the following criteria: At least 12 months since spontaneous menstrual bleeding; Prior documented hysterectomy and the surgical removal of fallopian tubes and ovaries; At least 55 years of age with prior hysterectomy with or without surgical removal of the ovaries; Aged 35 to 54 years with a prior hysterectomy without surgical removal of the ovaries or with a status of ovaries unknown with documented follicle-stimulating hormone level demonstrating elevation in postmenopausal range.

 

2. Women without prior breast cancer, but who are at elevated risk for breast cancer: Histologically confirmed lobular carcinoma in situ treated by local excision only or at least 1.66% probability of invasive breast cancer within 5 years using Breast Cancer Risk Assessment Profile; No clinical evidence of malignancy on physical exam within the past 180 days; No evidence of suspicious or malignant disease on bilateral mammogram within the past year; No bilateral or unilateral prophylactic mastectomy and No prior invasive breast cancer or intraductal carcinoma in situ

Objectives: Determine whether Raloxifene is more or less effective than Tamoxifen in significantly reducing the incidence rate of invasive breast cancer in postmenopausal women; Evaluate the effects of Tamoxifen and Raloxifene on the incidence of intraductal carcinoma in situ, lobular carcinoma in situ, endometrial cancer, ischemic heart disease, fractures of the hip and spine, or Colles' fractures of the wrist in these participants; Evaluate the toxic effects of these regimens in these participants and Determine the effect of these regimens on the quality of life of these participants.

Sketch a comparative clinical trial to evaluate the drug Raloxifene (relative to the drug Tamoxifen) in reducing the incidence of breast cancer in postmenopausal women1 who are at increased risk of the disease2.

 

http://www.cancer.gov/star

Solution

Purpose of Treatment: The purpose of this study is to examine the performance of the drug Raloxifene (relative to the drug Tamoxifen) in reducing the incidence of breast cancer in postmenopausal women1 who are at increased risk of the disease2.

 

Eligible subjects are: 1. postmenopausal women at increased risk for developing invasive breast cancer, who meet one of the following criteria: At least 12 months since spontaneous menstrual bleeding; Prior documented hysterectomy and the surgical removal of fallopian tubes and ovaries; At least 55 years of age with prior hysterectomy with or without surgical removal of the ovaries; Aged 35 to 54 years with a prior hysterectomy without surgical removal of the ovaries or with a status of ovaries unknown with documented follicle-stimulating hormone level demonstrating elevation in postmenopausal range.

 

2. Women without prior breast cancer, but who are at elevated risk for breast cancer: Histologically confirmed lobular carcinoma in situ treated by local excision only or at least 1.66% probability of invasive breast cancer within 5 years using Breast Cancer Risk Assessment Profile; No clinical evidence of malignancy on physical exam within the past 180 days; No evidence of suspicious or malignant disease on bilateral mammogram within the past year; No bilateral or unilateral prophylactic mastectomy and No prior invasive breast cancer or intraductal carcinoma in situ. The eligible patients are briefed as to the details and potential risks and benefits of study participation, and those who give informed consent and who meet all inclusion and exclusion requirements are enrolled in the trial.

Study treatments include Raloxifene and Tamoxifen. Enrolled subjects are randomly assigned either to Raloxifene with PlaceboTamoxifen or to Tamoxifen with PlaceboRalixifene. Double-blinding is employed, so that neither the subjects nor the clinical workers know the actual individual treatment assignments.

Subjects are then followed for: Incidence of invasive breast cancer in postmenopausal women; Incidence of intraductal carcinoma in situ, Incidence of lobular carcinoma in situ, Incidence of endometrial cancer, Incidence of ischemic heart disease, Incidence of fractures of the hip and spine, and Incidence of  Colles' fractures of the wrist, Toxic effects of the medications, and Quality of Life.

Work all six (6) cases.