BNAD 276: Test 2

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

5%

for data that are normally distributed, the percentage of the data that falls within two standard deviation of the mean is...

95%

the central limit theorem states that, for any distribution, as n gets larger, the sampling distribution of the sample proportion - approaches a binomial distribution - becomes larger - approaches a normal distribution - becomes smaller

- approaches a normal distribution

the inverse transformation x= μ+zσ is used to: ___________ - calculate z values using known x values - compute x values for given probabilities - calculate probabilities using known x values

- compute x values for given probabilities

what is a primary requirement for a "good" sample? - it proves out hypothesis about the population - it is easy to analyze - it is representative of the population we are trying to describe

- it is representative of the population we are trying to describe

Central Limit Theorem

if the number of samples is greater than 30 the sampling distribution of those sample means will be normally distributed The theory that, as sample size increases, the distribution of sample means of size n, randomly selected, approaches a normal distribution.

parameter

a constant

estimate

a particulate value of an estimator

central limit theorem

allows us to say a camping distribution can be approximated as Normal is a sample size (n) reaches at least a certain number

selection bias

an underrepresentation of certain portions of the population

True or False: A parameter is a numerical measure that describes a sample

False: a parameter is a numerical measure that describes a population

statistic

random variable

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

time

continuous uniform distribution

uniform distribution that can be described by a continuous random variable many times can be seen in datasets that measure some element of time

the height of the probability density function f(x) of the uniform distribution defined on the interval [a,b] is....

1 / b-a between a and b, and zero otherwise

if standard error is a measure of dispersion, what happens to the dispersion as sample size (n) increases?

as n increases the dispersion (standard error) decreases a decreasing standard error means better estimates about the population parameters

example of continuous uniform distribution

assume you are on your own private Wifi network and the time it takes to load yourD2L home page is between 0 to 1 seconds. If it has an equal chance to take any time between 0 and 1 seconds, it would be described as a continuous uniform distribution

continuos distributions

based on a random variable describing an infinite amount of outcomes within an interval

if a sample statistic consistently over - under estimates a population parameter, than there is _____

bias

confidence intervals

consider the potential dispersion (variation) in a popoulation as well as a sample's size (n) in order to give a range of values where the true popoulation parameter might reside

suppose you were told that the delivery time of your new washing machine is equally likely over the time period from 9 am to noon. if we define the random variable X as delivery time then X follows the? - continuos uniform distribution - normal distribution - discrete uniform distribution - binomial distribution

continuos uniform distribution

stratified sampling

first categories/group your observations according to a predetermined rationale each group is called a stratum second randomly select a proportionally representative amount of observations from each group to obtain your sample this method gives the most precise estimates

cluster sampling

first categorize/group observations according to a predetermined rationale each group is called a cluster all the observations from each selected cluster are used for the sample this method gives the least precise results

in general, the variability between sample means is ______ the variability between observations - more than - equal too - less than - biased when compared to

less than

we can use the finite populate correction factor when

n ≥ 0.05N

if the shape of the population from which a simple random sample is drawn is normal, than the shape of the sampling distribution of x is - skewed - unknown - uniform - normal

normal

the expected value of X (with line on top) is equal to

population mean u

the expected value of p is the

proportion of success in the population

uniform distribution

regarded as the simplest type of distribution as it describes a set of data for which all values over a given range, have equal probability of occurring

In _________ the population is divided into strata and then randomly selected observations are taken proportionately from each stratum

stratified random sampling

if the standard deviation is unknown a _____ will be used

t-distribution

sampling distribution of sample means

the distribution of the varying sample means with varying numbers there will always be some sort of distribution

margin of error

the half width of a confidence interval, everything to the right of the +-

normal distribution

the most important and widely used distribution and can be doing in many applications; height, weight, length. yearly sales, time to market for a product.... used as an idealized model

a random variable X follows the continuous uniform distribution if.... - its probability distribution is bell shaped - its probability distribution is based on n independent trials - it has an equally likely chance of assuming any value within a specific range - it assumes the values 0, 1, 2.......,n with different probabilities

it has an equally likely chance of assuming any value within a specific range

the probability distribution of a continuous random variable is called its - probability density function - probability mass function - probability model function

robability density function

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

statistic parameter

all of the following are examples of random variable that likely follow a normal distribution EXCEPT - the weights of newborn babies - the scores on the SAT - the number of states in the USA - the debt of college graduates

- the number of states in the USA

simple random sampling

involved randomly selecting observations from the entire population every observation from the population has an equal chance of being selected some examples would be using a random number generator or names from a well shuffled hat

if we were to sample repeatedly from a given population, the average value of the sample means will equal - the sample mean minus the population mean, divided by the standard error of the mean - the population mean divided by the square root of n - the sample mean - the population mean

the population mean

the branch of statistics that uses samples statistics to estimate a population parameter or test a hypothesis about such a parameter is BEST referred to as... - hypothetical statistics - descriptive statistics - inferential statistics - correlated statistics

- inferential statistics

the value of the finite population correction factor is always - less than zero - less than one - equal to zero - greater than one

- less than one

the probability distribution of the sample mean is commonly referred to as the - sampling distribution of p - sampling distribution of x - sampling distribution of u - sampling distribution of o

- sampling distribution of x

the most practical way to reduce the margin of error is by - using cluster samples - increasing the confidence level - selecting a larger sample size - selecting a popoulation with a smaller standard deviation

- selecting a larger sample size

when attempting to estimate parameters with statistics, it is important to keep a few things in mind

- statistics are known - parameters are unknown - statistics are random - parameters are constant

stratified sampling is preferred to cluster sampling when the objective is - to reduce costs - to access every possible individual in the population - to increase precision

- to increase precision

cluster sampling works best - when most of the variation in a population is within groups and not between groups - when most of the variation in a population is between groups and not within groups - when there is variation in a population both with groups and between groups

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

if the interval is based on either a known standard deviation or proportion a _______ is used

z distribution (z-score)

the probability that a continuous random variable X assumes a particular value x is... - between zero and infinity - between zero and one - greater than one - zero

zero

which of the following is true about a sample statistic such as the sample mean or sample proportion? - a sample statistic is always known - a sample statistic is a random variable - a sample statistic is constant - a sample statistic is a parameter

- a sample statistic is a random variable

the central limit theorem states that, for any distribution, as n gets larger, the sampling distribution of the sample mean becomes

closer to a normal distribution

the total area under the normal curve is ____ - greater than 1 - equal to 1 - between -1 and 1 - less than 1

equal to 1

when a sample statistic is used to make inferences about a population parameter it is referred to as a ____

estimator

the z table provides the cumulative probabilities for a given z. what does cumulative probabilities mean? - the probability that Z is less than or equal to a given z value - the probability of the sum of two values of Z - the probability that Z is greater than or equal to a given z value - the probability that Z is equal to a given z value

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

selection biased occurs when - those responding to a survey or poll differ systematically from the non respondents - there is a systematic exclusion of certain groups from consideration for the sample - the population has been divided into strata - cluster sampling is used instead of strained random sampling

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

bias

when a statistic underestimates or overestimates a parameter

non response bias

when respondents of a poll or survey have very different types of responses than non respondents

consistency

when the value of the statistic eventually converges to the value of the parameter as 'n'

the area under a normal curve below its expected value is ______ - 0.50 - 0.75 - 1.0 - 0

0.50