Flashcards
Statistics 2 definitions
Flashcards do conjunto (39)
- 1What are the conditions of a binomial distribution?A fixed number of independant, success or failure trialswith a constant probability of sucess.
- 2What is E(X) for binomial distributions?np
- 3What is Var(X) for Binomial distributions?np(1-p)
- 4What is the mean and varience of a Poisson distribution?lambda for both
- 5What can 'n' in a binomial distribution also be called?The index
- 6What can 'p' in a binomial distribution also be called?The parameter
- 7What are the conditions for a Poisson distribution?Events must occurr...
singly in space or time
independantly of each other
at a constant rate - 8What are the conditions for approximating a Binomial with a Poisson distribution?n must be large and p ust be small
np<10 - 9If X-B(n,p) X can be approximated by Po(...)?Po(np)
- 10State the properties of a continuous random variable p.d.ff(x)>/= 0 since you cannot have negative probabilities
P9ab)= the area under the line between a and b
integrating f(x) between -ve and +ve infinity gives 1, since the total area under the curve is total probability which = 1 - 11What is the probability of a single value happening in a continuous probability distribution function?0
- 12What is E(aX+b)?aE(X) +b
- 13What is Var(aX+b)?a^2 x Var(X)
- 14If m is the median what must F(m)= ?0.5
- 15What is f(x) for a continuous uniform distribution?1/(b-a)
- 16What is E(X) for a uniform distribution?(a+b)/2
- 17What is Var(x) for a uniform distribution?(b-a)^2
______
12 - 18What are the conditions for approximating a Poisson with a normal distribution?Lambda must be large
- 19What are the conditions for approximating a Binomial with a normal distribution?n large
p close to 0.5 - 20How do you approximate Poisson with normal?X-N(lambda, lambda)
- 21How do you approximate binomial with the normal distribution?X-N(np, np(1-p) )
- 22Define a populationA collection of individual people or items.
- 23What is a census?An investigation in which information is obtained from all members of a population.
- 24Give 3 advantages of taking a censusEvery single member of a populatio is used
It is unbiased
It gives an accurate answer - 25Give 3 disadvantages of taking a censusIt takes a long time
It's expensive
It is often difficult to ensure the whole population is survyed - 26Define a sampling unitAn individual member of a populaion
- 27Give 3 disadvantages of a sampleThrere is uncertainty about sampling in that there will be a natural variation between any 2 sampes due to natural variation between individual units that make up the sample.
Bias can occurr if you sample from an incomplete sampling frame, or get responses only from people that have a particular interest in the topic being studied.
Bias can occur if the person taking the sample allows their personal feelings to influence choices. - 28Define a sampling frameA list of sampling units used in practice to represent a population.
It may be a list, file, index, map or database. - 29Give 4 advantages of samplingIf the population is large a well mixed sample will be representative of the whole population.
Sampling is cheaper than a census.
It is advantageous where testing of items results in their destruction.
When using a sample, data is generally more readily available. - 30Define: population parameterAny characteristic of a population which is measurable.
- 31Define: a parameterA numerical property of a sample
- 32What is a statistic?A quantity calculated soley from observations in a sample, and does not involve any unknown paraneters.
- 33Describe a sampling distributionA distribution defined by giving all possible values of the statistic and probabilities of each occurring by chance.
- 34Define: hypothesisA statement made about the vaule of a population parameter that we wish to test by collecting evidence in the form of a sample.
- 35What is a test statistic?A summary of evidence from a sample used in a statistical hypothesis test.
- 36Describe the null hypothesisThe hypothesis we assume to be correct unless proved otherwise.
- 37Describe the alternative hypothesisIt tells us about the nature of the population parameter if our assumption is proved to be wrong.
- 38Define the critical regionThe range of values of the test statistic that would lead you to rejecting H0.
- 39Define: critical valuesValues on the boundary of the critical regions
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- A2 level Maths FlashCards sobre Statistics 2 definitions, criado por J000D97 em 22-02-2015.
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