BNAD 276 exam 2

Chance variation

-Caused by a number of randomly occurring events that are part of the production process. - not controllable by the individual worker or machine - expected, so not a source of alarm as long as it's magnitude is tolerable and the end product meets specifications

Control Charts

-Developed by Walter A Shewhart - a plot of calculated statistics of the production process over time - production process is "in control" if the calculated statistics fall in an expected range - production process is "out of control" if calculated statistics reveal an undesirable trend

Assignable variation

-caused by specific events or factors that can usually be identified and eliminated - identified and corrected or removed

Parameters

A constant whose value may be unknown. Only one population.

Estimate

A particular value of the estimator.

Statistics

A random variable who's value depends on the chosen random sample. Used to make inferences about the population parameters.

Simple random sample

A sample of n observations which has the same probability of being selected from the population as any other sample of n observations

Estimator

A statistic that is used to estimate a population parameter

Sample

A subset of the population

nonresponse bias

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

selection bias

A systematic exclusion of certain groups from consideration for the sample

Margin of error

Accounts for the variability of the estimator and the desired confidence level of the interval. Formal definition: "the 1/2 width of a CI"

Normal Transformation (standardization)

Any normal distributed random variable X with mean u and standard deviation o can be transformed into the standard normal random variable Z

Sample statistic

Calculated from sample and used to make inferences about the population

Population

Consists of all items of interest in a statistical problem

Continuous Uniform Distribution

Describes a random variable that has an equally likely chance of assuming a value within a specified range

Probability Density Function

Describes the relative likelihood that X assumes a value within a given interval that add up to 1

Cluster sampling

Divide population into mutually exclusive and collectively exhaustive groups, called clusters

Stratified random sampling

Divide the population into mutually exclusive and collectively exhaustive groups, called strata

Sampling distribution

Each random sample of size n drawn from the population provides an estimate of u- the sample mean

Central Limit Theorem

For any population X with expected value u and standard deviation o, the sampling distribution of X will be approximately normal if the sample size n is sufficiently large

Bias

The tendency of a sample statistic to systematically over- or underestimate a population parameter

Acceptance sampling

Used at the completion of a production process or service. If a particular product does not conform to certain specifications, then it is either discarded or repaired

Finite population correction factor

Used to reduce the sampling variation of the sample proportion

Inverse transformation

you are given a probability and have to solve for x (value in raw data)

Standard normal table (Z table)

Gives the cumulative probabilities and negative values of

Width of a confidence interval

Influenced by sample size n, standard deviation o, and confidence level 100 (1-...)%

Detection approach

Inspection occurs during the process in order to detect any nonconformance to specifications. Goal is to determine whether the production process should be continued or adjusted before producing a large number of defects.

Statistical quality control

Involves statistical techniques used to develop and maintain a firm's ability to produce high-quality goods and services. Two approaches are acceptance sampling and detection approach

Cumulative density function

It shows how the sum of the probabilities approaches 1, which sometimes occurs at a constant rate and sometimes occurs at a changing rate

Standard Normal distribution

Mean is equal to zero and standard deviation is equal to one.

Standard deviation

Measure of dispersion for population

Standard error

Measure of dispersion for samples

Expected value

On average or over the long-term

Confidence interval

Provides a range of values that, with a certain level of confidence, contains the population parameter of interest

Normal distribution

Symmetric. Bell-shaped curve. Closely approximates the probability distribution of a wide range of random variables. Describes by two parameters u (the population mean which describes the central location of the distribution) and o^2 (the population variance which describes the dispersion of the distribution)

Discrete

The random variable assumes a countable number

Continuous

The random variable is characterized by uncountable values within any interval