 A committee on community relations in a college town plans to survey local businesses about the importance of students as customers. From telephone book listings, the committee chooses 150 businesses at random. Of these, 73 return the questionnaire mailed by the committee. What is the population for this sample survey? What is the sample?

Introduction to Statistics

Statistics is a way of reasoning, along with a collection of tools and methods, designed to help us understand the world. Statistics are particular calculations made from data

 Population data is used when you are gathering data from every individual of interest.  Ex: Asking the entire football team a question  Sample data is used when you are gathering data from some of the individuals of interest.  Ex: Asking only the offensive line a question and apply it to the entire football team Population Data or Sample Data?

A. Population B. Sample

A. Population B. Sample

A. Population Data B. Sample Data You want to know what sports teens prefer so you send out a survey to all the students in your high school.

A. Population B. Sample Population Data or Sample Data?

A. Population B. Sample Population Data or Sample Data?

A. Population B. Sample Population Data or Sample Data?

 A statistic is a descriptive measure computed from a sample of data.  A parameter is a descriptive measure computed from an entire population of data.  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.

A. Parameter B. Statistic

A. Parameter B. Statistic

 A committee on community relations in a college town plans to survey local businesses about the importance of students as customers. From telephone book listings, the committee chooses 150 businesses at random. Of these, 73 return the questionnaire mailed by the committee. What is the population for this sample survey? What is the sample?

 Survey – a questionnaire used to collect interesting data on a certain topic from a sample of people.  EX: You want to find out how many students in your class had a summer job.  EX: The government wants to determine average household income in the United States.  EX: You want to know if tattoos have an influence on a person’s GPA.

 Observational Study – we observe individuals and measure variables of interest but do not attempt to influence the responses. Observational Studies may show a correlation between variables, but cannot always guarantee causation.  EX: A study of child care enrolled 1364 infants in 1991 and planned to follow them through their sixth year in school. In 2003, the researchers published an article finding that “the more time children spent in child care from birth to age four-and-a-half, the more adults tended to rate them, both at age four-and-a-half and at kindergarten, as less likely to get along with others, as more assertive, as disobedient, and as aggressive.”

 Experiment – we deliberately impose some treatment on (that is, do something to) individuals in order to observe their responses. Experiments can carry more convincing evidence of a cause and effect relationship.  EX: “Take the Pepsi Challenge” – in the 80’s Pepsi had a huge marketing scheme that had people do a blind taste test to see which soda they preferred – Pepsi or Coke.  EX: Does Vitamin C reduce the causes of getting a common cold?

A. Survey B. Observational Study C. Experiment

A. Survey B. Observational Study C. Experiment

A. Survey B. Observational Study C. Experiment

A. Survey B. Observational Study C. Experiment

A. Survey B. Observational Study C. Experiment

 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.

 Random sampling: when everyone in a population has an equal chance of being chosen in the experiment.  Stratified sampling: when the population is first divided into similar categories and the number of members in each category is determined.  Systematic sampling: when you determine a method for which to choose members of the population (assign numbers to the population and then choose every 5 th person to participate)  Cluster sampling: when you randomly put the population into clusters and then choose a cluster randomly and ask the question of that cluster.

 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 5 th person to participate) Give every animal a random number and then choose every 5 th 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. Example if selecting 10 animals from 25 dogs, 15 cats, and 10 rabbits

A. Random B. Stratified C. Systematic D. Cluster 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.

A. Random B. Stratified C. Systematic D. Cluster A principal goes to one classroom in each department and chooses two students from each classes to participate in a school climate survey.

A. Random B. Stratified C. Systematic D. Cluster WSFCS sends out a survey to parents by generating a list of student numbers from PowerSchool.

 Some questions may use language that people can associate with emotions:  How much of your time do you waste on facebook?  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 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.

A. Biased B. Unbiased A person asks, “Do you prefer delicious pancakes or cold soggy cereal?

A. Biased B. Unbiased Asking people shopping at a farmer’s market if they think locally grown fruit and vegetables are healthier than supermarket fruits and vegetables.

A. Biased B. Unbiased A survey about whether or not teachers who earn their master’s degrees should be paid more is sent out to all teachers in NC.

 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.

Resources used:  "Next: Introduction to Data and Measurement Issues Surveys and Samples." CK-12 Foundation. N.p., n.d. Web. 21 Aug  Yates, Daniel S., David S. Moore, and Daren S. Starnes. The Practice of Statistics: TI-83/84/89 Graphing Calculator Enhanced. New York: W.H. Freeman, Print.  Greg Fisher – Mount Tabor High School  Christina Holst – Parkland High School  Wendy Bartlett – Parkland High School