Bus Stat Test 3 CH 7-8 concept questions from learnsmart

a 95% confidence interval for the population mean is constructed as 6 +- 2. what is the probability of error, a?

0.05

random samples of a size of 100 are taken from a population proportion is 0.40. the expected value sample proportion is. E(P)(P bar) = p

0.40

the confidence coefficient equals

1 - a

what is the value of z(a/2) for a 90% confidence interval for the population mean

1.645

the confidence level is equal to

100 * (1 - a) %

a 95% confidence interval for the population mean is calculated as (40, 80). the margin of error for this interval is

20

a 95% confidence interval for the population mean is calculated as (40, 80). the point estimate for this interval is

60

in a statistical problem, a population consist of

all items of interest

If the population from which samples are drawn is not normally distributed, then the sampling distribution of the sample mean is

always normally distributed

if a sample statistic consistently over- or under-estimates a population parameter, then there is

bias

involves dividing a population into mutually exclusive and exhaustive groups, called clusters, and then deleting a random sample from these clusters for analysis

cluster sampling

the standard error of the sample mean is NOT affected by the

confidence level

parameter

constant

what is a primary requirement of a "good" sample?

it is representative of the population we are trying to describe

Suppose you are constructing a confidence interval for the population mean. for a given confidence level and sample size, the width of the interval is wider for a

larger standard deviation

the value of the finite correction factor is always

less than one

the purpose of statical quality control is to

maintain high-quality goods and services

the parameter p represents the

population proportion

which of the following is a descriptive measure for a qualitative variable? standard deviation proportion mean median

proportion

the expected value of (P bar) is the

proportion of successes in the population

statistic

random variable

suppose you are constructing a confidence interval for the population mean. for a given confidence level and standard deviation, the width of the interval is wider for a

smaller sample size

in the population is divided up into mutually exclusive and collectively exhaustive groups called strata. the sample consists of randomly-selected elements from each stratum.

stratified random sampling

stratified sampling is preferred to cluster sampling when the objective is

to increase precision

(true or false) the t(df) distribution is bell-shaped and symmetric around 0.

True

___ is caused by a number of randomly occurring events that are part of the production process

Chance variation

nonresponse bias occurs when

Those responding to a survey or poll differ systematically from the non-respondents

(true or false) if we have access that included the entire population, then the values of the parameters would be known and no statistical inference would be required

True

When constructing a confidence interval for the population mean and the standard deviation of the sample is unknown, the degrees of freedom for the t distribution are defined as

n - 1

as a general guideline, the normal distribution approximation can be used to describe the sampling distribution of the sample mean when

n is greater than or equal to 30

which of the following is NOT a component of a control chart?

normal curve

a confidence interval narrows if the following is a accomplished

the chosen confidence level decreases the sample size increases

the sampling distribution of estimator follows a normal distribution when the underlying x bar population is normally distributed and/or when the sample size is large enough. as a "rule of thumb" we use the following to check sample size

n is greater than or equal to 30

in order to construct a confidence interval of mean (u), the sampling distribution of the estimator X bar must follow or approximately follow a(n) ____ distribution

normal

the sampling distribution of the sample proportion can be approximated by a normal distribution when

np is greater than or equal to 5 and n(1 - p) is greater than or equal to 5

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

point estimate +- Margin of error

the expected value of (X bar) is equal to the

population mean

the mean and standard deviation are often used to describe ____ data while the proportion is a descriptive measure that can also be used for ___ data

quantitative, qualitative

a confidence interval can be interpreted as

range of values used to estimate an unknown population parameter

the probability distribution of the sample mean is commonly referred to as the

sample distribution of (x bar)

assignable variation is caused by

specific events that can usually be identified and eliminated

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

statistic, parameter

Bias can occur in sampling. Bias refers to _______.

the tendency of a sample statistic to systematically over- or under-estimate a population parameter

Selection bais occurs when

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

a control chart is a plot of calculated statistics of a production process over

time

estimate

a particular value of an estimator

the central limit theorem states that, for any distribution of the sample mean becomes

closer to a normal distortion

(true or false) a production process is in control if the sample means on a control chart start below the centerline, tend upward, and do not cross the upper control limit.

false

a firm uses acceptance sampling when

it produces a product and at the end of the process, inspects a portion

the further a population proportion deviates from p = 0.50, the ____ the sample size required in order to satisfy a normal approximation

larger

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

margin of error

a certain type of light bulb is advertised to have a life of about 1000 hours of use. with a certain level of confidence, it is advertised that the illegitimates is between 90 and 110 hours. 100 hours is the point if estimate, then the margin of error is

10 hours

the general rule for using the finite correction factor is that the sample constitutes at least ___ of the population

5%

for a 95% confidence interval for the population mean, if samples of size n are drawn repeatedly from a given population, then

5% of the sample means will fall outside of the corresponding confidence interval

a population has a mean of 50 and a standard deviation of 10. a random sample of 144 is selected. the expected value of X bar is equal to

50

the green letter ___ denotes the level of significance

a