bus 245 exam 3

true or false: a parameter is a numerical measure that describes a sample

false

a statistic is a ______ _____ whose value depends on the ______ _____ _____

random variable; chosen random sample

bias is often caused by samples that are not ________ of the population

representative

a population consists of all items of interest in a statistical problem, whereas a ______ is a subset of the population

sample

what is the most commonly used sampling method?

simple random sample

we use a calculated sample ______ to make inferences about an unknown population __________

statistic; parameter

_____ sampling is preferred when the objective is to increase precision

stratified

the probability that a continuous random variable X assumes a particular value x is

zero

the probability distribution of a continuous random variable is called its probability ________

density function

true or false: the distinct values of both a continuous random variable and a discrete random variable can be counted.

false

a sample of n observations that has the same probability of being selected from the population as any other sample of n observations

simple random sample

basic type of sample that can be used to draw statistically sound conclusions about a population

simple random sample

includes randomly selected observations from each stratum

stratified random sampling

political pollsters often employ what sampling method?

stratified random sampling

the number of observations per stratum is proportional to the stratum's size in the population

stratified random sampling

the population is first divided up into mutually exclusive and collectively exhausted groups called strata

stratified random sampling

the sample consists of observations from each group

stratified random sampling

a normal random variable X is transformed into Z by

subtracting the mean, and then dividing by the standard deviation

what is the primary requisite for a "good" sample?

that it be representative of the population you are trying to describe

the fewer the degrees of freedom=

the broader the tails

the exponential distribution is related to which distribution?

the poisson distribution

selection bias occurs when

there is a systemic exclusion of certain groups from consideration for the sample

true or false: many different samples could be drawn from a population in order to analyze that population

true

in a statistical problem, a population consists of

all items of interest

states that the sum or average of a large number of independent observations from the same underlying distribution has an approximate normal distribution

central limit theorem

_______ sampling is preferred when the objective is to reduce costs

cluster

the sample consists of observations from selected groups

cluster sampling

each t distribution is identified by what?

degrees of freedom

the branch of stats that uses sample stats to estimate population parameter or test a hypothesis about such a parameter is best referred to as

inferential statistics

the allowed probability that an interval estimate of a population mean will not contain u is referred to as the

level of significance

a confidence interval is constructed by using the point estimate as a base, to which we add and subtract the

margin of error

a random variable X with an equally likely chance of assuming any value within a specified range is said to have which distribution?

continuous uniform distribution

determine the extent of the broadness of the tails of the distribution

degrees of freedom

the probability that a discrete random variable X assumes a particular value x is

between zero and one

a sample statistic is considered ________ if it systematically over or under estimates the unknown parameter being estimated

biased

a t distributions have slightly ______ ______ than the z distribution

broader tails

the population mean describes the _______ location

central

the probability that the estimation procedure will generate an interval that contains the population parameter of interest

confidence coefficient

provides a range of values that, with a certain level of confidence, contains the population parameter of interest

confidence interval

a population parameter is ________ although is value may be _______

constant; unknown

the population variance describes the _________ of distribution

dispersion

is exponential distribution symmetric?

no

refers to a systematic difference in preferences between respondents and nonrespondents to a survey or a poll

nonresponse bias

a graph depicting the normal probability density function is often referred to as what?

normal curve

the standard deviation of the sample mean

o/(sqrt)n

the variance of the sample mean

o^2/n

we use a sample statistic to make inferences about an unknown population

parameter

what is the most typical form of a calculated confidence interval?

point estimate +- margin of error

consists of all items of interest in a statistical problem

population

the expected value of the sample proportion is equal to what?

population proportion

a subset of the population

sample

we use what to make inferences about the unknown population parameter?

sample statistic

a family of distributions which are similar to the z distribution in that they are all bell shaped and symmetric around zero

t distribution

a particular value of the estimator is called what?

estimate

the normal distribution is _______ in the sense that the tails get closer and closer to horizontal axis but never touch it

asymptotic

normal probability distribution is _____ shaped and ______

bell; symmetrical

a confidence interval is generally associated with what?

margin of error

the probability distribution of a discrete random variable is called its probability _________

mass function

as sample size increase, the shaped of the sampling distribution of P becomes

more normal

the probability distribution of an estimator

sampling distribution

refers to a systematic underrepresentation of certain groups from consideration for the sample

selection bias

the tendency of a sample statistic to a systematically overestimate or underestimate a population parameter

bias

the mean, median, and mode are all ______ for a normally distributed random variable

equal

for a continuous random variable, one characteristic of its probability density function is that the area under over all possible values of x is

equal to one

the sample mean is commonly referred to as what?

estimator/expected value

t distribution is commonly referred to as

tdf

what does cumulative probability mean?

the probability that z is less than or equal to a given z value

true of false: if we had access to data that included the entire population, then the values of the parameters would be known and no statistical inference would be required

true

true or false: a confidence interval provides a range of values that should contain a population parameter with a certain level of confidence

true

the normal distribution is completely described by ____ parameters

two

the expected value of the sample mean

u