11 Flashcards
If random variables X and Y are independent, then the variance of R is?
Sigma_x ^2 + sigma_y ^2, but not Covariance.
Whenever you find the variance of R after adding or subtracting random variables, the sign is?
Always positive when adding the variances of each of the two random variables.
After you sample the population you?
Use the resulting sample to produce an estimate theta ^_n
What does theta ^ _n and theta mean?
Estimate, parameter
Estimater?
Method for making the estimate
Estimate?
Guess after you have collected the sample and followed the method.
Sampling design?
Procedure used to collect a sample from a population.
When talking about sampling, you assume that?
Every value in the sample was measured without error.
When we are sampling, the errors in our estimates using (theta ^ _n) occur only because a part of the population is included in the sample and may be biased or may exclude rare variables. This type of error is called?
Sampling error
Non-sampling errors?
Errors in your estimate that are not due to which sample was selected.
Example of non-sampling errors?
•Population sampled was different than the population of interest.
•Non-participation
•Non-response
•Poor measurement
•Detectability problems
An estimator (theta^ of theta) is unbiased for theta if its expected value is equal?
E(theta^) = theta, theta is the parameter of interest.
Biased sample is?
E(theta ^) - theta
If you were to repeat an unbiased sample theta^ again and again and is equaled to theta, then?
It’s unbiased.
If you have something unbiased, then its biased value will be?
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