Stats Exam 3

Question 1

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

Answer 1

Simple Random Sample (SRS)

Question 2

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

Answer 2

probability sample

Question 3

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

Answer 3

stratified random sample

Question 4

another word for subgroups

Answer 4

strata

Question 5

people in each stratum should be _______

Answer 5

similar

Question 6

sampling that uses probability sampling in a series of stages

Answer 6

multistage random sample

Question 7

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

Answer 7

Random Variable

Question 8

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

Answer 8

probability distribution

Question 9

the two main types of random variables

Answer 9

discrete and continuous

Question 10

characteristics of discrete random variables

Answer 10

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

Question 11

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

Answer 11

possible outcomes

Question 12

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

Answer 12

probability distribution

Question 13

the probabilities p must satisfy two requirements:

Answer 13

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

Question 14

a ___________ __________ _________ takes on all values in an interval

Answer 14

continuous random variable

Question 15

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

Answer 15

density curve

Question 16

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

Answer 16

density curve

Question 17

a continous random variable has _____ many possible values

Answer 17

infinitely

Question 18

all continuous probability models assign probability __ to every ________ outcome

Answer 18

0; individual

Question 19

statistical inference involves two prominent techniques:

Answer 19

confidence intervals, hypothesis tests

Question 20

What are the three Simple Conditions for Inference About a Mean

Answer 20

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

Question 21

the entire group of individuals that we want information about

Answer 21

population

Question 22

what we actually examine in order to gather information

Answer 22

sample

Question 23

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

Answer 23

simple random sample

Question 24

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

Answer 24

probability sample

Question 25

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

Answer 25

stratified random sample

Question 26

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

Answer 26

undercoverage

Question 27

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

Answer 27

nonresponse

Question 28

variable whose value is a numerical outcome of a random phenomenon

Answer 28

random variable

Question 29

this variable has a finite number of posisble values

Answer 29

discrete random variable

Question 30

the __________ of DRV lists the values and their probabilities

Answer 30

probability distribution

Question 31

this variable takes all values in an interval of numbers

Answer 31

continuous random variable

Question 32

the probability distribution of continuous random variables is described by a

Answer 32

density curve

Question 33

the probability of any event is the area under

Answer 33

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

Question 34

a number that describes the population

Answer 34

parameter

Question 35

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

Answer 35

parameter

Question 36

a number that describes a sample

Answer 36

statistic

Question 37

the value of this can change from sample to sample

Answer 37

statistic

Question 38

we often use a statistic to estimate an unknown

Answer 38

parameter

Question 39

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

Answer 39

sampling distribution

Question 40

the center of the sampling distribution

Answer 40

bias

Question 41

a statistic used to estimate a parameter is unbiased if

Answer 41

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

Question 42

the variability of a statistic si described by the

Answer 42

spread of its sampling distribution

Question 43

this spread of sampling distribution is determined by

Answer 43

the sampling design and the sample size of n

Question 44

statistics from larger probability samples have

Answer 44

smaller spreads

Question 45

to reduce bias, use

Answer 45

random sampling

Question 46

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

Answer 46

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

Question 47

to reduce the variability of a statistic from an SRS,

Answer 47

use a larger sample

Question 48

you can make the variability as small as you want by

Answer 48

taking a large enough sample

Question 49

the purpose of a confidence interval

Answer 49

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

Question 50

any confidence interval has two parts:

Answer 50

an interval computed from the data and a confidence level

Question 51

the interval often has

Answer 51

the form estimate +- margin of error

Question 52

the margin of error is obtained from

Answer 52

the sampling distribution

Question 53

what does the margin of error indicate

Answer 53

how much error can be expected because of chance variation

Question 54

the confidence level states the

Answer 54

probability that the method will give a correct answer

Question 55

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

Answer 55

95% of your intervals will contain the true parameter value

Question 56

the margin of error of a confidence interval decreases as

Answer 56

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

Question 57

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

Answer 57

test of significance

Question 58

the hypotheses are stated in terms of

Answer 58

population parameters

Question 59

the test of significance is based on

Answer 59

a test statistic

Question 60

the p-value is

Answer 60

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

Question 61

small p-values indicate

Answer 61

strong values against H0

Question 62

calculating p-values requires

Answer 62

knowledge of the sampling distribution of the test statistic

Question 63

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

Answer 63

significant at significance level a

Question 64

the power of a significance test measures

Answer 64

its ability to detect an alternative hypothesis

Question 65

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

Answer 65

increases