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
