Bell Ringer 12-12-16 In your own words define the following: 1. Convenience 2. Random 3. Stratified 4. Systematic 5. Cluster

(ways to collect data) Monday, December 12, 2016 Sampling Methods (ways to collect data) Monday, December 12, 2016

Inferential Statistics Inferential statistics enables you to make an educated guess about a population parameter based on a statistic computed from a sample randomly drawn from that population.

Sampling When conducting a survey, experiment, or observational study, it is almost impossible to survey everyone in a population so people use various sampling methods to gather information. One major concern about sampling methods is whether it is a biased or unbiased method to gather information.

Convenience sampling: Sampling Methods Convenience sampling: when those chosen as a sample of the population are chosen due to ease of collecting data. SIMPLE EASY (first 5 people) NOT a “good” method…

Sampling Methods Random sampling: when everyone in a population has an equal chance of being chosen in the experiment.

Sampling Methods Stratified sampling: when the population is first divided into similar categories and the number of members in each category is determined.

Sampling Methods Systematic sampling: when you determine a method for which to choose members of the population (assign numbers to the population and then choose every 5th person to participate)

Sampling Methods Cluster sampling: when you randomly put the population Into clusters and then choose a Cluster randomly and then randomly choose people in that cluster to participate.

Randomly selecting 10 from all 50 animals Example if selecting 10 animals from 25 dogs, 15 cats, and 10 rabbits Random sampling: when everyone in a population has an equal chance of being chosen in the experiment. Randomly selecting 10 from all 50 animals Stratified sampling: when the population is first divided into similar categories and the number of members in each category is determined. Select 5 from 25 dogs, 3 from 15 cats and 2 from the rabbits Systematic sampling: when you determine a method for which to choose members of the population (assign numbers to the population and then choose every 5th person to participate) Give every animal a random number and then choose every 5th number Cluster sampling: when you randomly put the population into clusters and then choose a cluster randomly and then randomly choose people in that cluster to participate. Randomly put the animals into 2 groups of 25, choose a group, and then choose 10 from that selected group.

Which sampling method is used in the scenario below? A Gallop poll surveyed 1,018 adults by telephone in each region of the country, and 22% of them reported that they smoked cigarettes within the past week. Random Stratified Systematic Cluster

Which sampling method is used in the scenario below? A principal goes to one classroom in each department and chooses two students from each classes to participate in a school climate survey. Random Stratified Systematic Cluster

Which sampling method is used in the scenario below? WSFCS sends out a survey to parents by generating a list of student numbers from PowerSchool. Random Stratified Systematic Cluster

Biased Questions Some questions may use language that people can associate with emotions: How much of your time do you waste on Snap Chat? Some questions may refer to a majority or supposed authority: Would you agree with the NCAE that teachers should be paid more for earning their master’s degree? Phrased awkwardly: Do you disagree with people who oppose the ban on smoking in public places?

Sampling Bias Sampling Bias occurs when one or more sub groups of a population are either over represented or under represented when conducting a survey or experiment. Using the appropriate sampling method for the question reduces bias. Discuss with your partner some examples of bias that could occur when choosing a sample from a population. Be prepared to share your examples.

Activity: Martha wants to construct a survey that shows which sports students at her school like to play the most. List the goal of the survey. What population sample should she interview? How should she administer the survey? Create a data collection sheet that she can use to record her results.

What is needed to determine causation for the population   Random Selection No Random Selection Random Assignment Causality Population Only to sample No Random Assignment No causality No results!

Classwork: Samples & Stats Homework: Sampling Procedures Practice Assignments Classwork: Samples & Stats Homework: Sampling Procedures Practice

Exit Ticket In your Math Journal, write a summary of the past 2 days lessons. You may write a paragraph or make a list with examples. Show your work to Mrs. Leahy before exiting the classroom.