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).
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 scan-the 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 Chi-square 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
a.Is the presence of the carrier related to whether tonsils are enlarged or not. Test this hypothesis at the P(Type I error)=a=.05 level.
b. Calculate a 95% confidence interval for the difference between the Tonsils enlarged probabilities in the presence of the carrier versus that in the absence of the carrier.
2.In a controlled clinical trial to determine the efficiency of an experimental drug for treating migraine headache, patients were divided into four groups and were treated with four drugs: A, B, C and D. Each treatment lasted 12 weeks. At the end of the treatment period, the effect of the drug was classified into two categories: effective and not effective. The migraine headache data obtained are as follows:
Use these data to run a chi-square 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 pre-employment 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 pre-employment test to those who did not initially pass the pre-emplyment test. For this test use P(Type I error)=a=.05.b. Calculate a 95% confidence interval for the above difference.
2.A survey was made of 164 customers in a department store. These customers were divided into four groups with members of each group viewing only one of the four types of advertisements available for a certain product. The total numbers of customers who made purchases by viewing group are given below.
Can we determine from this whether there is a difference in the purchase fraction across the four groups?