JUST ANSWER QUESTION 2 1. In the fall of 2011 VCU launched Spit for Science: the
ID: 3315127 • Letter: J
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JUST ANSWER QUESTION 2
1.In the fall of 2011 VCU launched Spit for Science: the VCU Student Survey (www.spit4science.vcu.edu). This project is following the 2011 VCU freshman class across its college years, and will also enroll new VCU freshman classes over the next few years. The goal of the project is to understand how genetic and environmental factors come together to influence a variety of health-related outcomes in the VCU undergraduate population.
Data was collected on multiple days, and of interest is to estimate µ = the mean number of students from which data has been collected each day since the project began. For this problem only, assume that the standard deviation of the number of students from which data has been collected each day since the project began for all days is 12.3 students. What is the minimum number of days that would need to be selected for data collection to allow the calculation of a 90% confidence interval with margin of error no greater than 4.1 students? Please circle your final answer. (5pts)
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2. Croutons, Salads and Wraps is another tenant of Laurel and Grace Place. Of interest is to estimate = the proportion of all VCU students who have eaten food from Croutons, Salads and Wraps. To estimate this proportion a 99% confidence interval will be calculated and the goal is that the margin of error will be no larger than .046. What is the minimum number of current VCU students that would need to be selected to allow the calculation of a 99% confidence interval with margin of error no greater than .046? Please circle your final answer. (5 pts)
Explanation / Answer
a.
Compute Sample Size
n = (Z a/2 * S.D / ME ) ^2
Z/2 at 0.1% LOS is = 1.645 ( From Standard Normal Table )
Standard Deviation ( S.D) = 12.3
ME =4.1
n = ( 1.645*12.3/4.1) ^2
= (20.23/4.1 ) ^2
= 24.35 ~ 25
b.
Compute Sample Size ( n ) = n=(Z/E)^2*p*(1-p)
Z a/2 at 0.01 is = 2.576
Sample Proportion = 0.5
ME = 0.046
n = ( 2.576 / 0.046 )^2 * 0.5*0.5
= 784 ~ 784
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