Flashcards
Lecture 2
Flashcards do conjunto (16)
- 1What is an inference?An inference is a formal name that is given to learning from data using statistical tools. (conclusion reached from evidence and reasoning)
- 2What is the population?The population is a complete set of entities or elements or units or subjects that we wish to describe or make an inference about. It can be real or hypothetical. And well defined or not well defined
eg pop of nz=everyone living in nz.
pop of the class=everyone in the class - 3What is a sample? What do we do to ensure theres no bias?A sample is a subset of the population. We use random selection. We want it to be representative (similar to the population that is being studied) and also non biased.
If random sampling isnt possible, we would then have to assume that our sample is representative - 4What is a sampling frame? How do we ensure that theres no bias if there is no list?This is a list of items in a population from which a sample is drawn.
This rarely coincides with our population of interest.
eg. telephone roles list of people etc.
We can ensure an unbiased sample as long as every individual has the same chance of being drawn - 5What is a parameter?A parameter is a fixed number that characterises a population. (Eg the average height of everyone in the room)
Parameters can either be known/unknown, hypothetical or real. It is usually represented by a greek letter - 6What is a random variable?A random variable is an unknown quantity that varies in an unpredictable way. When a random variable is observed, it is referred to as an observed/realised value
- 7What is a discrete random variable?A variable that can be put into one to one correspondence with the counting numbers.
No decimals! Whole numbers - 8What is a continuous variable?A variable that can be expressed on a continuous scale in which every value is possible
- 9What is a Categorical variable?A variable that is restricted to one of a set of categories.
Eg heads or tails
It is for things that dont have a numerical value - 10What does the lower case roman letter mean in relation to random variables?Lower case roman letter represents the observed/realised value
- 11What does P(X=x) mean?The probability that the random variable X takes the Value x
- 12What are random variables described by?Probability distributions
- 13What are observed values of random variables?They are data
- 14What is a statistic?A numerical summary of data
(bar x=mean) - 15What is an estimate?A statistic used as an intelligent guess for a parameter
Estimates often have a circumflex ^.
(mu is a parameter) - 16What is a model?A model is a mathematical description of the data generating mechanism. They are mainly based on parameters. Eg the tossing of heads or tails can be modelled by a Bernoulli distribution
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- University Statistics FlashCards sobre Lecture 2, criado por arielhchen em 31-07-2015.
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- arielhchen
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