ISDS Exam 2
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