STA
6166 UNIT 3 Section 3 Exercises

Welcome  <  Begin  <  <  Unit 3 Section 3 Exercises  >  Unit 3 Test 
You can choose to work some or all of the problems listed below. We recommend that you at least work the problems listed in your major area of interest. Answers to these exercises can be found here. (ANSWERS).
General Questions. 
Using this equation, compute the following probabilities. Back in Exercise 4.28 we were presented with a table describing the results of a radiological determination test for presence of Appendicitis. Suppose this study had been redone with 220 patients suspected of having appendicitis being subjected to the radiological determination test (CAT scanthe experimental approach) as well as to a clinical assessment (the expensive but definitive answer). Only two posible choices are available for each method, a decision of definitely apendicitis (DA) or definitely not appendicitis (DNA). The result of this study is in the table below.
Using these data do the following: 

For students in agriculture and environmental fields. 
1. An experiment is run to examine two different methods methods of preserving onions. The researcher proposes to compare Method A to Method B, by storing a large number of onions using each method and after 6 months to classifying each onion as 'good' or 'defective'. The result of the experiment is as below:
a. Use these data to test whether the proportion of GOOD onions in each method are different from each other. Use a=.05. b. Calculate a 95% confidence interval for the difference tested above. 2. A second aspect of the study was to examine the effects of different
fertilizer treatments on the incidence of blackleg (Bacterium phytotherum)
on potato seedlings. Seedlings were randomly assigned to a fertilizer
treatment and after three weeks classified as to whether it was contaminated
by blackleg or free. The results for four treatment were as follows:
Use these data to determine if the presence of Blackleg is independent of the Fertilization method. Use a=.05. 

For students in engineering fields. 
1. A project manager for an engineering firm submitts a bid for engineering
design for two projects. The firm formally evaluates the chances that
each bid will be accepted by surveying its engineers. The following
table summarizes the collective assessment from this survey.
a. Test whether the chances that each bid was accepted are different. Use a=.05. b. Calculate a 95% confidence interval for the difference of chances that each bid was accepted.
Use these data to run a Chisquare test to determine whether a finding of low level is independent of the factors used. Use a=.05. 

For students in toxicology and health science fields. 
1. In a study of children aged 0 to15, concern is focused on the presence
or absence of the carrier for Streptococcus Pyogenesis
and the relationship between the presence of the carrier and tonsil
size.
b.
Use these data to run a chisquare test to determine whether the effectiveness
of all drugs are the same.This is equivalent to testing that all effectiveness
proportions are the same. 

For students in community development, education and social services fields.  1. A company uses a preemployment test to screen applicants
for sales jobs. We are interested in whether the screning test is effective.
In an experiment, a random samples of applicants
who pass the test and a second sample of those who do not pass the screening
test are all employed. The number of employees who successfully completed
the training program in these two samples was recorded as follows.
a. Test whether the proportions of employee who successfully completed the training program is the same for the group who initially passed the preemployment test to those who did not initially pass the preemplyment test. For this test use P(Type I error)=a=.05. b. Calculate a 95% confidence interval for the above difference.
Can we determine from this whether there is a difference in the purchase fraction across the four groups? 