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WorksheetsApril 13th
Total questions: 5
Worksheet time: 15mins
Name
Class
Date
1.
Random Variables (8)
Suppose X and Y are random variables with E(X) = 780, var(X) = 75, E(Y) = 430, and var(Y) = 25. Given that X and Y are independent, what is the variance of the random variable X - Y?
Suppose X and Y are random variables with E(X) = 780, var(X) = 75, E(Y) = 430, and var(Y) = 25. Given that X and Y are independent, what is the variance of the random variable X - Y?
a)
A) 75 - 25
b)
B) 75 + 25
c)
C) √(75 - 25)
d)
D) √(75 + 25)
2.
Maria wants to know if birds prefer to eat in one place over another. She makes three feeders out of 2-liter bottles and paints all of them red. She fills each of the feeders with the same amount of mixed birdseed, and plans to keep the feeders out for 10 days before measuring how much seed is eaten from each feeder. She puts each of the feeders in her back yard: one feeder in a large dead tree, another feeder she sits on the dog house, and the last she sits in a small bushy tree.
What is the dependent variable?
What is the dependent variable?
a)
Length of the birdfeeders
b)
Amount of time feeders are outside
c)
Amount of seed eaten
d)
Location the feeders are put in.
3.
One hundred rats with mothers that were exposed to high levels of tobacco smoke during pregnancy were put through a simple maze. At the outset, the maze required the rats to make a choice between going left and going right. Eighty of the rats went right when running the maze for the first time. Assume that the 100 rats can be considered an SRS from the population of all rats born to mothers who were exposed to high levels of tobacco smoke during pregnancy. (Note that this assumption may or may not be reasonable, but researchers often assume that lab rats are representative of large populations, since they are often bred to have uniform characteristics.) Let p be the proportion of rats in this population that would go right when running the maze for the first time. A 90% confidence interval for p is
a)
0.8 ± 0.040.
b)
0.8 ± 0.078.
c)
0.8 ± 0.066.
4.
You are thinking of using a t procedure to construct a 95% confidence interval for the unknown mean μ of a population for a random sample taken from the population. You suspect that the distribution of the population is not Normal and may in fact be moderately skewed. Which of the following statements is then correct?
a)
You should not use the t procedure, since the population does not have a Normal distribution.
b)
You can use the t procedure provided that n>30 .
c)
You can use the t procedure regardless of the sample size since t procedures are robust against non-Normality.
5.
Which of the following statements is FALSE?
a)
The power of the test increases as α increases.
b)
The power of a test does not depend on the sample size.
c)
The power of a test is the complement of a Type II error.
d)
As the α-level increases, P(Type II error) decreases.
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