Chapter 20 - Chance Errors in Sampling Flashcards
What is the expected value for the sample percentage of a simple random sample?
The expected value for the sample percentage is equal too the population percentage.
What is the difference in the population percentage and the sample percentage?
The chance error is included in the sample percentage is the difference in the randomness of the sample compared to the actual population percentage.
How do you compute the Standard Error of X?
SD * Square root of n
What happens to the sample error percentage as the sample gets larger?
The sample error percentage decreases when a sample size is multiplied by a factor, it increases by the square root of that factor thus as n gets larger. our actual estimate gets closer to the true proportion due to the Law of Averages.
What happens to the standard error for the number as the sample size gets larger?
The standard error increases slowly relative to the sample size.
The Correction Factor
How is accuracy determined?
When estimating percentages, the absolute size of the sample is what determines the accuracy not the size of the sample relative to the population.
- Only true if the sample is a small portion of the population.
Is Simple Random Sampling with or without replacement?
A Simple Random Sample means drawing at random without replacement.
When must the Correction Factor be used?
When the sample is a substantial size fraction of the population or drawing without replacement.
What is the Correction Factor formula?
Square root:
of tickets in box - # of draws
________________________
number of tickets in box - 1
Central Limit Theorem
When drawing at random with replacement from a box, the probability histogram for the sum or average will eventually follow the normal curve no matter what the box contents look like.
What is p?
Population proportion and is usually what we are interested in finding.
What is p hat?
Sample proportion or percentage.
p hat = p + chance error
What is n?
Sample size
What happens to a sample average as n gets larger?
X bar or the sample average gets closer to the actual proportion average because as n gets larger the standard error gets smaller.
What is X bar?
box average + chance error.
