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PT Elements > Stats Exam 3 > Flashcards

Stats Exam 3 Flashcards

1
Q

every individual in the population has an equal chance to be selected

A

Simple Random Sample (SRS)

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2
Q

Sample in which every individual in the population has a chance (greater than zero) to be selected in the sample.

A

probability sample

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3
Q

sometimes the sample contains several subgroups, these subgroups make up different proportions of the population

A

stratified random sample

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4
Q

another word for subgroups

A

strata

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5
Q

people in each stratum should be _______

A

similar

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6
Q

sampling that uses probability sampling in a series of stages

A

multistage random sample

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7
Q

Variable that takes numerical values that describe the outcomes of some random process

A

Random Variable

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8
Q

the ___________ ______________ of a random variable gives its possible values and their probabilities

A

probability distribution

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9
Q

the two main types of random variables

A

discrete and continuous

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10
Q

characteristics of discrete random variables

A

able to list all possible outcomes; assign probabilities to each outcome

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11
Q

in general a discrete random variable X takes a fixed set of ___________ ___________

A

possible outcomes

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12
Q

the ____________ ___________ lists the outcomes xi, and their probabilities pi

A

probability distribution

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13
Q

the probabilities p must satisfy two requirements:

A
  1. every probability p1 is a number between 0 and 1
  2. the sum of the probabilities is 1
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14
Q

a ___________ __________ _________ takes on all values in an interval

A

continuous random variable

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15
Q

the probability of distribution x with a continuous random variable is described by a _________ _________

A

density curve

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16
Q

the probability of any event is the area under the _____ _______

A

density curve

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17
Q

a continous random variable has _____ many possible values

A

infinitely

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18
Q

all continuous probability models assign probability __ to every ________ outcome

A

0; individual

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19
Q

statistical inference involves two prominent techniques:

A

confidence intervals, hypothesis tests

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20
Q

What are the three Simple Conditions for Inference About a Mean

A
  1. SRS from the population of interest. No nonresponse or other practical difficulty.
  2. The variable is exactly normally distributed N(u,o)
  3. The population mean u unknown, but the population standard deviation o known
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21
Q

the entire group of individuals that we want information about

A

population

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22
Q

what we actually examine in order to gather information

A

sample

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23
Q

sample of size n that consist of n individuals from the population chosen in such a way that every set of n individuals has an equal chance to be the sample actually selected

A

simple random sample

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24
Q

sample chosen by chance. we must know what samples are possible and what chance each possible sample has

A

probability sample

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25
Q

to select this sample, first divide the population into groups of similar individuals, called strata. then choose a separate one of these sample in each stratum and combine these samples to form the full sample

A

stratified random sample

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26
Q

occurs when some groups in the population are left out of the process of choosing the sample

A

undercoverage

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27
Q

occurs when an individual chosen for the sample can’t be contacted or does not cooperate

A

nonresponse

28
Q

variable whose value is a numerical outcome of a random phenomenon

A

random variable

29
Q

this variable has a finite number of posisble values

A

discrete random variable

30
Q

the __________ of DRV lists the values and their probabilities

A

probability distribution

31
Q

this variable takes all values in an interval of numbers

A

continuous random variable

32
Q

the probability distribution of continuous random variables is described by a

A

density curve

33
Q

the probability of any event is the area under

A

the density curve and above the values of x that make up the event

34
Q

a number that describes the population

A

parameter

35
Q

a fixed number, but in practice we do not know its value

A

parameter

36
Q

a number that describes a sample

A

statistic

37
Q

the value of this can change from sample to sample

A

statistic

38
Q

we often use a statistic to estimate an unknown

A

parameter

39
Q

the distribution of values taken by the statistic in all possible samples of the same size from the same population or randomized experiment

A

sampling distribution

40
Q

the center of the sampling distribution

A

bias

41
Q

a statistic used to estimate a parameter is unbiased if

A

the mean of its sampling distribution is equal to the true value of the parameter being estimated

42
Q

the variability of a statistic si described by the

A

spread of its sampling distribution

43
Q

this spread of sampling distribution is determined by

A

the sampling design and the sample size of n

44
Q

statistics from larger probability samples have

A

smaller spreads

45
Q

to reduce bias, use

A

random sampling

46
Q

when we start with a list of the entire population, simple random sampling produces unbiased estimates –

A

the values of a statistic computed from an SRS neither consistently overestimate nor consistently underestimate the value of the population parameter

47
Q

to reduce the variability of a statistic from an SRS,

A

use a larger sample

48
Q

you can make the variability as small as you want by

A

taking a large enough sample

49
Q

the purpose of a confidence interval

A

to estimate an unknown parameter with an indication of how accurate the estimate is and how confident we are that the result is correct

50
Q

any confidence interval has two parts:

A

an interval computed from the data and a confidence level

51
Q

the interval often has

A

the form estimate +- margin of error

52
Q

the margin of error is obtained from

A

the sampling distribution

53
Q

what does the margin of error indicate

A

how much error can be expected because of chance variation

54
Q

the confidence level states the

A

probability that the method will give a correct answer

55
Q

if you use 95% confidence intervals, in the long run

A

95% of your intervals will contain the true parameter value

56
Q

the margin of error of a confidence interval decreases as

A

the confidence level C decreases, the sample size n increases, and the population standard deviation decreases.

57
Q

intended to asses the evidence provided by data against a null hypothesis in favor of an alternative hypothesis

A

test of significance

58
Q

the hypotheses are stated in terms of

A

population parameters

59
Q

the test of significance is based on

A

a test statistic

60
Q

the p-value is

A

the probability that the test statistic will take a value at least as extreme as that actually observed

61
Q

small p-values indicate

A

strong values against H0

62
Q

calculating p-values requires

A

knowledge of the sampling distribution of the test statistic

63
Q

if the p-value is as small or smaller than a specified value a, the data are statistically

A

significant at significance level a

64
Q

the power of a significance test measures

A

its ability to detect an alternative hypothesis

65
Q

increasing the size of the sample _______ the power when the significance level remains fixed

A

increases

PT Elements (43 decks)

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