# get out homework. get out notes

Post on 24-Feb-2016

34 views

Category:

## Documents

Tags:

• #### set of n individuals

Embed Size (px)

DESCRIPTION

Get out homework. Get out notes. Designing Samples. Section 5.1 Continued. Sample Designs. A simple random sample (SRS) of size n contains n individuals from the population chosen so that every set of n individuals has an equal chance of being selected. Sample Designs. - PowerPoint PPT Presentation

TRANSCRIPT

PowerPoint Presentation

Get out homework.

Get out notes.Section 5.1 ContinuedDesigning SamplesSample DesignsA simple random sample (SRS) of size n contains n individuals from the population chosen so that every set of n individuals has an equal chance of being selected.Every individual has an equal chance. Every set has an equal chance. 3Sample DesignsExample: SRS or not?I want a sample of nine students from the class, so I put each of your names in a hat and draw out nine of them.Does each individual have an equal chance of being chosen?

Does each group of nine people have an equal chance of being chosen?Yes for both. So yes on SRS.4Sample DesignsExample: SRS or not?I want a sample of nine students from the class but I know that there are three juniors and 17 seniors in class, so I pick one junior at random and eight seniors.Does each individual have an equal chance of being chosen?

Does each group of nine people have an equal chance of being chosen?

No, juniors more likely than seniors. No, because we cant have nine seniors. Not an SRS.5Sample DesignsBetter than a hat: Software can choose an SRS from a list of the individuals in a list.Not quite as easy as software, but still better than a hat: a table of random digits.Computers.Sample DesignsA table of random digits is a long string of the digits 0 9 with two properties: Each entry in the table is equally likely to be any of the ten digits 0 through 9The entries are independent of each other. (Knowing one part of the table tells you nothing about the rest of the table.)

TABLE B in the back of your book.Sample DesignsEach entry is equally likely to be 0 9Each pair of entries is equally likely to be 00 99Each triple of entries is equally likely to be 000 999And so on