ISDS ch 7 and 9

a sample can provide results more quickly and for a lower cost. In some cases taking the population is not a viable option, so decision makers can only rely on info obtained from sample. If a sample is selected properly, a sample can provide more reliable results than taking a census.

why do we take a sample instead of a census

to make conclusions about the population based upon a single sample Ex: political pollsters: the sample proportion is used to estimate the actual proportion of the votes that each candidate will get from the population of voters

main goal of inferential statistics

random variable

a statistic is a ______whose value depends on these chosen random samples

selected bias

a systematic under representation of certain groups from consideration for the sample

not equal to, > , <

alternative hypothesis uses what signs regarding population parameters

census and survey

are used to represent a population and sample

simple random sample most statistical methods presume

basic type of sample that can be used to draw statistically sound conclusion about non population is

if i'm pulling a sample from a population that is unknown distribution, then the sample will be normally distributed if it is sufficiently large n> or = 30

central limit theory says what about a sample mean

- a control chart plots the sample estimates - all sample estimates are plotted with reference to a center line -have upper and lower control limit which indicate excessive deviation above or below expected value

characteristics of all charts

c chart

chart that monitors the count of defects per item, such as the number of blemishes on a piece of furniture

r chart and s chart

chart that monitors the variability of production process

statistical quality control

involved statistical techniques used to develop and maintain a firm's ability to produce high quality goods and services.

parameter

is a constant even though its value maybe unknown

what is simple sample random

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

p chart

is a useful chart to asses a population based on a sample

sample distribution

is the probability distribution of the sample mean x

survey data

is used to analyze government and business activities

reject the null or do not reject the null

We either ____ or _____ the null hypothesis

the sample distribution is normal if the sample size is sufficiently large np> 5 and n>(1-p)

central limit theorem for sample proportion says:

x chart

chart that monitors central tendency of a production process

the sampling distribution of the relevant estimator is normal

control chart is only valid if

three standard deviations

control limits are _____ from the centerline

non response error

error incurred when some subjects refuse to respond to a survey

what is a sample and what is it used for

it is a subset of the population. A sample statistic is used to make inferences about the unknown population parameter

identical

no two products are

coverage error

occurs when certain items are excluded from the sampling frame

x, r,s chart

quantitative control charts

bias

refers to the tendency of a sample stat to systematically over or underestimate a population parameter, often caused by samples that are not representative of the population

detection approach

the preferred method of quality control. Inspects the production process and determines whether production process should be continued or adjusted before a large number of defects are produced

the standard error of the sample mean

the standard deviation of the sample mean is called

standard error of the sample proportion

the standard deviation of the sample proportion is called

stratified random sampling

type of sample where population is divided into mutually exclusive and collectively exhaustive groups called strata. It includes randomly selected observations per stratum. The number of observations per stratum is proportional to the stratum's size in the population. the data from each stratum are eventually pooled.

assignable variation

type of variation caused by specific events or factors that can usually be identified and eliminated

as the sample size increases

when will a sample size that is not normally distributed begin to look normal

making statistical inferences

****probability sample is necessary when

probability sample Ex: simple random sample

sample in which items are selected based upon known probabilities

null hypothesis

Ho=

Type II error, where the probability of making a Type II error is denoted by β.

If we accept the null hypothesis when in reality the null hypothesis is false, we commit a

Type I error, where the probability of making a Type I error is denoted by α.

If we reject the null hypothesis when in reality the null hypothesis is true, we commit a

one tailed

____ is used when we can reject the null hypothesis only on one side of the hypothesized value of population parameter

two tailed

_____ is used when we can reject the null hypothesis on either side of the hypothesized value of population parameters

estimate

a particular value of a statistic is

non probability sample Ex: Convenience sample

a sample in which the items have unknown probabilities of being selected

always less than one; when N is large relative to n the finite correction factor is close to one and the correction factor isn't negligible

correction factor is

non sampling error (bias)

error that results in a distortion of conclusions

non response error

estimating percentage of car crashes that involve alcohol. Drunk drivers usually refuse the BAC test. What type of error

used to reduce the sampling variation of the sample mean. n> .05 N

finite population correction for sample mean says

the population from which the sample is drawn is normally distributed

for any sample size, the sample distribution is normal if

adjustment of production process is likely necessary

if calculated stats reveal an undesirable trend, then

controlled

if the calculated statistics a fall in an expected range, the product process is

standard error

sample size and ____ have an inverse relationship

statistical inference

where we examine the problem of estimating population parameters or testing hypothesis about such parameters

=,> =,<=

a null hypothesis uses what signs regarding population parameters

alternative hypothesis

Ha=

p chart

chart that monitors proportion of defectives in production process

chance and assignable

two types of variation

measurement error

CDC Hepatitis survey, teacher evaluation requiring you to fill in your name, order of survey questions. What type of error

type 1: the medical test says they have a disease, but they really don't (false positive) type 2: the medical test shows they don't have the disease, but they actually do. (false positive)

H0: A person is free of a particular disease Ha: A person has a particular disease explain type 1 and type 2

type 1: verdict found guilty, but really innocent type 2: verdict found them innocent, but are actually guilty

H0: An accused person is innocent Ha: An accused person is guilty what is type 1 and type 2 error?

reduce non response rate

most effective way to deal with non responsive bias is to

no statistical inference would be needed

population consist of all items of interest in a statistical problem. If we had access to data that encompasses the entire population then the values of the parameters would be known and

p and c chart

qualitative control charts

sample

since it is generally not feasible to gather info on the whole population,_______is used to to make a statistical inference

stratified consists of observations from each group and is preferred when objective is to increase precision. cluster consists of observations from the selected groups and is preferred when the objective is to reduce cost

stratified vs. cluster

non response bias

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

of the sample its based on

the credibility of a statistic depends on the quality of

sample error (as soon as you look at anything less than the entire population, you are not going to report 100 percent accuracy characteristic if the population)

the error incurred by taking a sample instead of a census

the population mean this means the sample mean is an unbiased estimator of the population mean

the expected value of the sample mean equals

equal to the population proportion

the expected value of the sample proportion is

many possible samples of a given size can be drawn from the population

there is only one population ,but

non response, coverage error, measurement error

three types of non sampling error

control chart commonly used in quality control

tool used to monitor the behavior of the production process

accepting sampling and detection approach

two approaches are used for quality control

accepting sampling

type of quality control used if it produces a product and at the completion of the production process, firm inspects a portion of the products. If it doesn't conform to specifications it is discarded or repaired, Problem is not all products are detected

cluster sample

type of sampling where population is divided into clusters (such as geographic areas). It includes observations from randomly selected clusters

chance variation

type of variation caused by number of randomly occurring events that are part of the production process. Not under the control of the individual worker or machine

estimator

when a statistic is used to estimate a parameter it is called

measurement error

when data collected do not reflect the true measurements

bias

when the info of a sample is not typical of info of population in a systematically way we say that a _____ has occured