Stats unit 4

p

population proportion

p hat

sample proportion

Multistage sampling

Using multiple methods to divide into groups, then select one or more groups, and then repeat until the sample is chosen

Voluntary response sample

Ask individuals to do something to respond to the survey

Convivence sampling

Asking people who are more convenient to contact

Quota sampling

Sampling widely used in opinion polling and market research, NO ASPECT OF RANDOMNESS

Proportion confidence interval

Estimates a population proportion

Normally distributed for proportions

n*p >_ 10 AND n(1-p) >_ 10

Normally distributed for means

n >_ 30 OR is stated as normal in the problem

The higher the level, the ________ the interval

Wider

Sampling error

No matter how well conducted

Different samples given different sample statistics

Inferential Stats

Used to make predictions or inferences

Descriptive Stats

Summarize and describe characteristics

Sample data 3 conditions

1) Randomly selected

2) Independent

3) Distributed normally

Higher confidence = ___________

Larger sample size = _______________

Wider interval

Narrower interval

Critical value

Multiplier based on the confidence level

Higher confidence=larger critical value

Confidence level

How confident the method is, such as 90%, etc

Cluster sampling

Population is divided into clusters, accurately reflect characteristics, then random sample is chosen

Stratified random sampling

Population is divided into groups based on similar characteristics, then a random sample from each strata is chosen

Systematic sampling

Picking every “nth” person or item

Simple random sample

A sample in which every possible sample of the desired size has an equal chance of being selected

Census

A complete count of the entire population

A statistic describes a _______, a parameter describes a ________.

Sample

Parameter

Random

The sample was selected at random

Normal

The sampling distribution must be approx. normal

Independent

One observation should not affect another

Proportion test

Testing a claim about a population proportion

Mean with sigma known

Mean CI/Test when population standard deviation is given

Mean with s given

Mean CI/Test when only sample standard deviation is given

Point estimate

The sample statistic in the center of the interval, such as p hat or x bar

Margin of error

How far you add/subtract from the point estimate

S or Sx

Sample standard deviation

Mu

Population mean/claimed mean

Sigma

Population standard deviation

n

Sample size

Alpha or a

Significance level

x bar

Sample mean