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2. Spirit Week Survey Results
1) What grade are you in?
6 9thgraders,610thgraders, 13 11thgraders, 15 12th graders
2) On a scale of 1-5,1 being the lowest, how much did you enjoy
taking part in spirit week?
3 said 1, 6 said 2, 11 said 3, 11 said 4, and 9 said 5
3) How do you feel that spirit week affected your school
spirit?
9unchanged10slight increase15average increase 6 great
increase
4) If you were to choose one, what was your favorite event?
18 said Lip-synching 8 Color Day 5 Powderpuff
1Homecoming 8 Decade Day 0 Penny Wars
3. Spirit Week Survey Results
5) If you were to choose one, what was your least favorite
event?
3 said Lip-synching 1 Color Day 1 Powder puff
1Homecoming 9Decade Day 25 Penny Wars
6) On a scale from 1-5,one being the lowest, how much did you like
the idea of each grade having a homecoming nominee?
23 said 1, 4 said 2, 6 said 3, 3 said 4, 4 said 5
7) How much did you participate in spirit week?
4 said Very Little20 said Somewhat 6 said A Lot
8) Did spirit week take away from your class time?
18 said Yes22 Said No
9) IF you answered yes to question 8, were your
teachers__________?
6 said Not Understanding8 said Somewhat Understanding 4 said Very
Understanding
4. What was your favorite event of spirit week?
5. What was your least favorite event of Spirit Week?
6. Our Survey
The population was the whole school, approximately 650
people.
The size of our sample was 40 people. Our sample was collected by
going into classrooms and having the first 40 people we saw fill
out our survey.
Our design was convenience sampling with a voluntary
response.
7. Controlled ExperimentsBlock Design
Anexperimentis a study in which the investigator imposes a change
or treatments on one or more groups. When the study involves two or
more groups, we say that it is acomparative experiment. The purpose
of an experiment is to determine the effect of the
independentexplanatoryvariables on a dependent response
variable.
Experiments are performed onunits.Human units are called
subjects.
Acontrol groupgenerally consists of the units who are not to
receive thetreatmentthat is the focus of the experiment. The other
group is called thetreatment groupsince units in the treatment
group receive the treatment.
A major challenge in the experimentation is to design the
experiment so that the explanatory variables are notconfounded.
Technically, two variables are confounded if the investigator
cannot separately identify their effects on the response variable.
One potential source of confounding is the effect oflurking
variables. A lurking variable is a variable that has an effect on
the response variable but is not measured as part of the study of
interest.
The determination of a relationship between the response variable
and the explanatory variables, sometimes calledfactors, is the
focus of the experimental process. A treatment is a combination of
specific values of each of the factors; these values are often
calledlevels.
8. Block Design
When an investigator expects that one specific characteristic of
the experimental units will likely affect the results of the
experiment, ablock designis appropriate.
Ablock designis similar to the procedure of selecting a stratified
sample that we considered in the sample survey section. In both
cases, either strata or blocks are created to control for the
effects of one or more lurking variables. Then, assignment into
groups within the strata or blocks is accomplished randomly using
probability. The goal of these techniques is to make the groups
being compared as similar as possible apart from the
treatment.
A useful blocking strategy is thematched pairs design.In this
design, data from two variables are paired in order to control for
lurking variables.
9. Chapter 4 Planning a Study
Four major types of collection strategies:
-Census
-Sample Survey
-Controlled Experiment
-Observational Study
10. Chapter 4 Sec 1 Basic Terminology and Census
Population-The entire collection of objects you are interested
in.
Parameters-Statistical measures that are computed regarding the
characteristics of a population.
Sample-A subset of the populations.
Statistics- Statistical measures calculated about a sample.
Census- A method of data collection in which all members of a
population are included in the survey.
11. Chapter 4 Sec 2 Sampling
Statistical Inference: The process of drawing conclusions about the
nature of the entire population based on the data from a
sample.
Sample design: Refers to the technique employed to select a subset
of a participants from the population and gather the data from the
population. Here are the 4 types of sample designs:
Voluntary Response: A general appeal is made for responses to one
or more questions.
Convenience Sampling: Members of the population are chosen based on
the convenience of including them.
Quote Sampling: Interviewers are assigned to interview a fixed
quota of members of the population.
Sampled Random Sampling (SRS):Involves selecting individuals at
random from the population without replacement. A sample of size n
is to be chosen from the population, where every chance in
equal.
12. 4.2 Continued
However, the first 3 types of sampling techniques above are flawed
because they may be biased. Bias is a systematic error that favors
a particular segment of the population or tends to encourage only
certain outcomes in the data. Simple Random Samples are usually
expensive to conduct and inconvenient, especially with large
populations.
3 other acceptable methods of sampling which uses probability in
its selection process is:
Stratified Random Sample: Divide the population into groups of
individuals that are similar in some way.
Multi Stage Cluster Sample: Method in which the population is
divided into a number of groups from which samples are drawn; these
are then divided into groups from which samples are drawn once
again and etc.
Systematic Sample: Everynth item is included in the sample. Like
every 4thor 7th.
Bias can arise in several ways.
Sampling Frame: The lost of possible subjects who could be selected
in a sample. If the sampling frame is not equal to the population,
the sample will be biased in the way the sampling frame is
biased.
Sampling errors can be summarized in three categories:
Random Sampling Error: Error that occurs because of chance
variation.
Sampling Method Error: Error that occurs because of the choice of
sampling method.
Non-Sampling Method Error: Error that occurs in the responses by
members in he sample.
13. Chapter 4 Sec 3Controlled Experiments
Experiment A study in which the investigator imposes a change or
treatment on one or more groups.
Comparative Experiment- When the study involves 2 or more
groups.
The purpose of an experiment is to determine the effect of the
independent explanatory variables on a dependent response variable.
Experiments are performed on units. Human units are called
subjects.
A control group generally consists of the units who are not to
receive the treatment that is the focus of the experiment. The
other group is called the treatment groups since units in the
treatment group receive the treatment. The determination of a
relationship between the response variable and the explanatory
variables, sometimes called factors, is the focus of the
experimental process. A treatment is a combination of specific
values of each of the factors: the values are often called
levels.
The three major requirements forcontrolled experiment:
-comparison
-randomization
-replication
14. 4.3 Continued
Comparison: Control group is used. In a drug trial, one unit is
place under a variable drug and the other under a placebo, a
treatment that should have no physical effect on the unit.
Randomization: Assigning units to control and treatment groups
using probability.
Replication: Experimental results are attempted to be replicated or
just repeated testing is done with larger numbers to see if chance
variance can be reduced.
The principles of experimental design are:
Control: Using a control helps us find the variables in the
experiment and find differences in the response variable.
Randomization: Assign units into a control group like placebo and
treatment groups to make sure they are similar as possible before
the treatment begins.
Replication: Repeat the experiment and attempt to replicate the
results on many units to reduce chance variance.
15. Chapter 4 Sec 4Observational Studies
In an observational study, a researcher collects information about
a population by measuring a variable of interest.An important
difference between observational studies and experiments is the
nature of any conclusion. If an experiment is correctly designed
and conducted, causation between the explanatory and response
variables can be concluded. A correctly designed and conducted
observational study only provides evidence of an association
between explanatory and response variables.
In order to control for sources that are confusing, most studies
strive to identify treatment and control groups that are the
same.
The difference betweena sample survey and observational study is
that in a sample survey the subject is asked for an opinion and in
an observational study the investigator observes and collects data
about the behavior.
16. Chapter 4 Test
1) Which of the following is true?
IA simple random sample is any sampling technique where each
element of the population has the same chance of being
selected.
IIA simple random sample is a sample where every set of n elements
in the population has the same chance of being selected.
IIIFrom a population of N=30, there are 60 equally likely possible
samples of size 3 if we are sampling with replacement.
A. I only
B. II only
C. III only
D. I and II only
E. None of the above
2) Creating a sample of children by starting with the third name in
the directory and selecting every 8th name best describes:
A.Random sampling
B.Systematic sampling
C.Convenience sampling
D. Stratified sampling
E.Multi stage cluster sampling
3) Which of the following are true statements?
IA census aims to contain only a portion of the entire
population.
IIStatistics is a statistical measure that is computed regarding
the characteristics of a population.
IIIThe sample size is too large relative to the population size to
conduct the sample.
A. I only
B. II only
C. I and II only
D. II and II only
E. None of the above
17. Chapter 4 Test
4) Which of the following are true statements?
IA census aims to contain only a portion of the entire
population.
IIStatistics is a statistical measure that is computed regarding
the characteristics of a population.
IIIThe sample size is too large relative to the population size to
conduct the sample.
A. I only
B. II only
C. I and II only
D. II and II only
E. None of the above
5) A measurable characteristic about an entire population is
A. A census
BA population
CA parameter
DA statistic
EA sample
6) Which of the following is not a source of bias in sample
surveys?
A.non-response
B.Wording of questions
C.Voluntary response
D.Use of a telephone survey
E.All are sources of bias
18. Chapter 4 Test
7) A randomized block design is similar to which of the following
sampling designs?
Simple Random Sample (SRS)
Convenience Sample
Systematic Sample
Stratified Sample
Cluster Sample
8) The 3 principles of experimental design include:
control, replication, homogeneity
randomization, control, homogeneity
Simple Random Sample, replication, homogeneity
Control, Randomization, Replication
9) Which of the following can be used to show a cause and effect
relationship between two variables?
A parameter
An observational study
A sample survey
A controlled experiment
A cluster sample
10) A newspaper in Montana conducted a poll of its readers on their
opinions about if Tiger Woods will continue with golf. 70 % of
their readers took part in this survey. This is an example of
A sample survey
An experiment
An observational study
A systematic random sample
A cluster sample
19. Chapter 4 Test
11) To conduct a survey of local businesses, a researcher opens the
yellow pagesto a random page, closes his eyes, puts his finger down
on the page, and then reads off the next 50 businesses. Which of
the following are true statements?
I. The survey incorporates chance.
II. The procedure results in a simple random sample.
III. The procedure could easily result in selection bias.
(A) I and II
(B) I and III
(C) II
(D) I,II, and III
(E) None of the above.
Open Ended:
1) What is the difference between observational study and sample
survey?
2) Describe the advantages and disadvantages of a Simple Random
Sample.
20. Bohan Questions
1.C
2.A
3.C
4.We think an observational study is possible. First, you can take
the three brands and make a bad of popcorn, but make sure that each
bag contains a specific amount of kernels. Therefore, you can
control the amount of popcorn being popped and then count the
kernels that didnt pop. With those numbers you can determine the
percentage of popcorn that didnt pop, and thus determine the best
brand.
1.C6. BE11. E A
2.C7. D12. E
3. AB8. E13. D
4. E9. E14. A E
5. C10. E15. D C or B
1)
a. To chose the same number of freshmen, sophomores, juniors, and
seniors, you could do a convenient sample of ten students in each
grade.
b. Use convenient sampling again, but use five girls and five boys
out of the ten in each grade.
c. If there are no restrictions, conduct a convenient simple random
sample of 40 students.
21. Controlled Experiment
Example of a control.
A group of 40 peopleof the same body fat percentage and life
stylesare taken intoacholesterollevelreducingdrug trialfor a
drugVYTORINto see the effects of the drug on cholesterol levels of
the individuals. A sample of 10is taken and given the same meal
plan and exercise routine for one week and then cholesterol levels
areread as the following, in mg/dL:
11511712710311911010510799121
The sample group is then placed on VYTORIN, the first 5 subjects on
a placebo and the remaining 5 on the treatment, acholesterol level
reducing drug, levels are once again taken:
11311511910511811010010597119
Verify that:x1112,s1=9 ,x2 110 , s2= 8
22. Blocking in Controlled Experiment
Example of block design.
The group of 40 is divided in 3 age groups, 18-25, 26-35, 36-45.
Five are taken from each group and levels are taken once again.
Three of the subjects are placed on the treatment and two on the
placebo from each group and levels are taken. The results of the
three groups are compared to each other and a result is drawn if
the drug affects aged group differently.
23. What we learned
We learned a great amount from this project because it involved so
many different parts. The first part was a process that including
making a survey, distributing it, and then calculating the results.
We learned that surveys are a great way to gather information about
a myriad of things. Surveys help other people determine a
populations opinions and thoughts, or gather other types of
information about a particular subject. By conducting surveys,
people can take steps to make effective changes.
In addition, we also learned about how effective the Block Design
can be. Block design is similar to selecting a stratified sample.
Blocks and strata are both created to control the effects of
lurking variables. We learned that block design can be very
effective when dealing with one characteristic of the experimental
units. By using blocks, results are more precise.
24. Feedback
We really enjoyed doing this project together as a group. It made
us realize all the effort and hard work it takes to conduct a
survey. We suggest that you continue to give this project to your
statistic students in the future. There was no part of the project
we disliked, even though we are not that bright at answering the
Bohan questions. However, he will make us use our noggin more and
become smarter Statisticians.