stats test 3

what is the confidence level if a=.10

90%

which of the following is true about a sample statistic such as a sample mean or sample proportion?

a sample statistic is a random variable

what does not describe both z and t

binomial distribution

for a continuous random variable x, the number of possible values

cannot be counted

population

consists of all interests

parameter

constant

each t distribution is identified by its

degrees of freedom

alpha is referred to as

level of significance

purpose of statistic quality control is ?

maintain high quality goods and services

which is not a component of a control chart

normal curve

estimate

particular value of an estimator

what is the most typical form of a calculated confidence interval

point estimate +- margin of error

expected value of x bar should be equal to

population mean

what is a descriptive measure for qualitative data

proportion

chance variation

random occurring events

statistic

random variable

a confidence interval narrows if the following is accomplished

sample size increases, the chosen confidence level increases

width for a interval is wider for a

smaller sample size

assignable variation

specific events that can be identified

We use a calculated sample _____ to make inferences about an unknown population _____.

statistic, parameter

what kind of sampling is used by political pollsters to make sure each religious group is represented?

stratified random sampling

selection bias

systematic differences between the test group and the control group due to a biased selection process

the mean of a normal standard distribution is equal to

zero

which of the following continuous distributions are positively skewed and bounded below zero?

exponential distribution, lognormal distribution

a 95% confidence interval for the population mean implies that

for a repeated samples 95% of the sample means will fall within the interval

a T distribution

has slightly broader tails than the z distribution

the sample size required to approximate the normal distribution depends on

how much the population varies from the normality

bias refers to

tendency of a sample statistic to over or under estimate

when estimating the population mean, the t distribution is used when

the population variance is unknown

selection biased occurs when

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

non bias occurs when

those responding to a survey or poll differ from non respondents

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

true

cluster sampling works best when?

when most of the variation in a population is within groups and not between groups