ISDS Exam 2

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Standard Error

The standard deviation of the sample mean

Bias

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

What are samples statistics used for?

To make inferences about the unknown population parameter

What are the types of errors we consider in the context of hypothesis testing?

Type I Type II

In a two tail-test what is important?

Upper AND lower tail

In a one tail-test what is important?

Upper OR lower tail

Finite population correction factor for the sample mean

Used to reduce the sampling variation of the sample mean

finite population correction factor for the sample proportion

Used to reduce the sampling variation of the sample proportion

Estimator

When a statistic is used to estimate a parameter

When is the CLM for the sample mean justified?

When n is greater than or equal to 30

When is Stratified sampling preferred?

When the objective is to increase precision

Social-desirability bias

refers to a systematic difference between a group's "socially acceptable" response to a survey or poll and this group's ultimate choice

P with a line over it

sample proportion

A hypothesis test can be what?

One-tailed or two-tailed

What chart is used for Qualitative Data?

P-chart

What are the most effective ways to deal with Nonresponse bias?

to reduce nonresponse rates by paying attention to survey design, wording, and ordering of the questions cant increase the response rate

When would a firm use acceptance sampling?

if it produces a product and at the completion of the production process, the firm then inspects a portion of the products

Using the Decision rule, we do not reject the null hypothesis when?

if the p-value is greater than or equal to alpha

Type II Error

is made when we do not reject the null hypothesis when the null hypothesis is false

Using the Decision rule, we reject the null hypothesis when?

of the p-value is less than alpha

How are Bias caused?

By samples that are not representative of the population

The expected Value of the sample proportion

Equal to the population proportion the sample proportion is an unbiased estimator of the population proportion

When is an estimator unbiased?

If its expected value equals the population parameter

When is the CLM for the sample proportion justified?

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

What is the difference between Stratified and Cluster Sampling?

In Stratified the sample consists of observations from each group, whereas in cluster sampling, the sample consists of observations from the selected groups

Statistical Quality Control

Involved statistical techniques used to develop and maintain a firms ability to produce high-quality goods and services

What chart is used for Quantitative Data?

X-chart

Sample

a subset of the poulation

Chance variation

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

Two-tail test

we can reject the null hypothesis on either side of the hypothesized value of the population parameter

One-tail test

we can reject the null hypothesis only on one side of the hypothesis value of the population parameter

When is cluster sampling preferred?

when the objective is to reduce costs

When the population standard deviation is know what table do we use?

z-table

Parameter

A constant, although its value may be unknown

Estimate

A particular value of the estimator

Statistic

A random variable whose value depends on the chosen random sample

Simple Random Sample

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

Selection Bias

A systematic underrepresentation of certain groups from consideration for the sample

Control Chart

A tool used to monitor the behavior of a production process

What are the two approaches used for statistical quality control?

Acceptance sampling Detection approach

What is the type I Error symbol?

Alpha

What is the type II Error Symbol?

Bravo

How would a firm use the detection approach?

By inspecting the production process and determines at which point the production process does not conform tho specification

Assignable variation

Caused by specific events or factors that can usually be identified and eliminated

What are the two types of variation that can occur?

Chance variation Assignable variation

Type I Error

Committed when we reject the null hypothesis when the null hypothesis is actually true

Population

Consists of all items of interest in a statistical problem

The Standard Deviation of the Sample Proportion

Referred to as the standard error of the sample proportion

Nonresponse bias

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

What is an unbiased estimator of the population mean?

Sample mean

X with line over it

Sample mean

What sampling methods do most statistical methods presume?

Simple Random Sample

Alternative Hypothesis (Ha)

Something has changed Sample evidence to contradict Ho

Central Limit Theorem

States that the sum or average of a large number of interdependent observation from the same underlying distribution has an approximate normal distribution

Null Hypothesis (Ho)

Status quo (how the population is, suppose to be having)

What are the steps in the Four Step procedure using the p-value approach?

Step 1. Specify the null and the alternative hypothesis Step 2. Specify the significance level Step 3. Calculate the value of the test statistic and the p-value Step 4. State the conclusion and interpret results

When the population standard deviation is unknown what chart do we use?

T-table

What is the most commonly used statistical tool in a quality control?

The Control Chart

What approach is preferred to quality control?

The detection approach

Stratified Random Sampling

The population is divided into mutually exclusive and collectively exhaustive groups called strata TheThe stratified sample includes randomly selected observations from each stratum The data from each stratum is pooled

Cluster Sampling

The population is first divided up into mutually exclusive and collectively exhaustive groups, called clusters. A cluster sample includes observations from randomly selected clusters

Sampling distribution

The probability distribution of the sample mean

Significance level

The probability of making a type I error


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