1.6 Sampling Methods

Question 1

Define Sample Survey

Answer 1

A sample survey selects a sample(cross0section) from the population of all individuals about which desire information. Sample surveys are sometimes called cross-sectional studies

Question 2

What is inference?

Answer 2

Drawing conclusions about a population on the basis of sample data.

Question 3

What are the two bad sampling method and give an example for each one. Why are these sampling methods bad?

Answer 3

Convenience Sample- choosing individuals who are around or those that are convenient to talk to
1.) sampling the first 30 people that enter the library and ask them about their study times
2.) sampling people you see in the mall about shopping habits

Voluntary Response Sampling - people who choose themselves by responding to a general appeal.Its where individuals choose to participate in a survey or study based on their own willingness or interest.
1.) Online Opinion Polls
2.) Call-in Radio Shows
3.) Comment Sections or Online Reviews

These samples are bad methods because they create bias

Question 4

Define Bias

Answer 4

Prejudice in favor of against one thing, person, group,etc. The design of a statistical study will show bias if it systematically favors certain outcomes( i.e, if it consistently overestimates or underestimates)

Question 5

What are the 4 types of bias that can happen in a sample)

Answer 5

1.) Voluntary Response Bias - people are eager to volunteer when they have a strong opinion on the matter.

2.) Response Bias - anything in a survey that influence respondents lying, trying to please the interviewer, unwillingness to reveal facts, leading or confusing questions.

3.) Nonresponse Bias - when a large amount of those sampled do not respond. (When you were selected but you chose not to respond/particulate or did it answer the door or phone or mail back questionnaire)

4.) Undercoverage Bias - sampling in a way that leaves out a certain portion of the population that should be in the sample. (Telephone polls, registered voter lists, etc)

Question 6

What are the 4 best sampling methods?

Answer 6

1.) Simple Random Sample (SRS) - every experimental unit and every possible sample has the same chance of being picked. (Flipping coin, rolling a die,names in a hat,etc)

2.) Stratfied Random Sample (SRS) - divides the population into smaller groups( strata) with something in common and then apply a SRS to each strata(gender, grade, age, etc)

3.) Systematic Random Sample (SRS) - sample selected at a random starting point but with a fixed periodic interval.(sampling a large neighborhood.start by picking a house at random and then survey every 10th house from there..Selecting every 5th person that walks through the door.)

4.) Cluster Sample (SRS) - population is broken down into groups, then all members of one or more groups are taken as the sample.(sample ALL students in a grade…Choose a bus at random and survey everyone on the bus.)

Question 7

What is the value that is calculated about a sample and the value that calculated a whole population is called?

Answer 7

For a population, that value is called a parameter and for a sample, that value is called a statistic