AP Statistics!!! Test Review 2014

Sampling Error ◦ Occurs in the act of choosing the sample ◦Undercoverage – certain members of population are ‘left out’  Suppose we use poll people a group of people at a golf tournament about how they feel about the Affordable Care Act… Non Sampling Error ◦ Occurs after sample is chosen ◦Non response – cannot be surveyed or refuse to answer question. ◦Response Bias ◦Poorly Worded Questions

Which type of error is made when you use phone calls to sample people, but you call during working hours? ◦Answer: Non Response (non sampling error) Which type of error is made when you use a telephone to sample people? ◦Answer: Undercoverage (sampling error) What type of error is shown below: ◦Question: “How do you feel that the extremely expensive Affordable Care Act will help you and your family’s overall health and wellness?” ◦Answer: It is a poorly worded question (non- sampling error) and will UNDERESTIMATE the support for the A.C.A.

Review of Chapter 4 Vocab Voluntary Response Sample ◦Participants ‘choose’ or volunteer themselves (not random; very biased) Convenience Sample ◦We only include who is ‘convenient’ to survey. (not truly random; biased) Simple Random Sample (SRS) ◦Every person has an equal chance to be selected (“all the names are in ‘one pot’”) DO NOT BREAK INTO GROUPS!!! Stratified Random Sample ◦Population is divided into groups or ‘strata’ that are made up of similar individuals within each group. You do an SRS within each group. Systematic Sample ◦We sample every ‘kth’ person after the first person is randomly selected. Multi-Stage Sample ◦Done on a large scale; combining other types of sampling methods; you sample to choose GROUPS, then sample within the groups. Cluster Sample ◦Population is divided into groups that don’t necessarily all look alike; the clusters should ‘mirror the population; you sample to choose GROUPS, then take a census within the group.

Simple Random Samples (“chopping through #’s) ◦Labels  9 people? ◦ 1 digit  10 people? ◦ 1 digit  100 people? ◦ 2 digits  57 people? ◦ 2 digits  1000 people? ◦ 3 digits  124 people? ◦ 2 digits

You have two dogs, each of whom have a litter of 12 puppies. You want to determine the amount of weight gain over 12 weeks based on the type of food that you give them. If you give puppy food #1 to one dog’s 12 puppies and puppy food #2 to the other dog’s 12 puppies and then compare the weight gain after 12 weeks, what type of experiment have you carried out? ◦Answer: An experiment, but NOT completely randomized

Puppies… continued… Suppose you now give puppy food #1 to an SRS of 6 puppies from one ‘momma dog’ and an SRS of 6 puppies from the other ‘momma dog’, with the remaining 12 puppies from the two ‘momma dogs’, then what type of design have you used now? ◦Answer: Block Design, based on which ‘momma dog’

Explain Double-blind experiments …. Single-blind… Be able to identify what these types of experiments look like and why we prefer to using ‘blinding’ in certain instances…

S Suppose that you decide to do a survey in Somerset to inquire about a ‘particular issue’. You decide to select an SRS of 50 homes in the city limits and you contact them for a face-to-face interview that consists of 2 questions. What is the chance that all 50 homes just happened to be drawn from the same neighborhood (Oaklawn)? ◦Answer: the same chance as for any other set of 50 homes….

You wish to do a survey of residents in the state of Tennessee. You select an SRS of 100 adults heads of households in each county in the state and ask their opinion on the selected topic. What type of sample is this? ◦Answer: Stratified

Does the amount of sales of ice cream (in dollars) accurately predict the number of drowning's in Lake Michigan? Does ice cream CAUSE drownings? Consider what conclusion can be drawn? ◦Answer: Lurking/confounding variable – seasonal variation in temperature… hotter it is, more ice cream consumed…. More people swim…. Thus, more drownings…

An experiment will take place at Kroger, in which participants will taste test each of two kinds of sweet tea. What type of design is this? ◦Answer: Matched Pairs

I choose to do a survey at Somerset High School. I randomly select 2 homerooms per grade and ask every student in those homerooms the selected question. What type of sample is this? ◦Answer: Cluster… (sample, then census)

I decide to do a large-scale sample using Gallup. I want to gather information about feelings about a potential major candidate for the U.S. presidency. I then select 10 states, and then within those 10 states, I select 2 AREA CODES and then select 200 people randomly from those AREA CODES to be a part of the survey… What type of sample is this? ◦ANSWER: Multi-stage

I decide to do a survey at the University of Alabama. I decide to divide the student population into groups based on the following criteria ◦In-state and in what 5 different regions from Alabama they are from ◦Out-of-state ◦I will then do random samples within each of the 6 groups. ◦What type of sample have I done? ◦ANSWER: Stratified

Why is doing an SRS of 100 people preferable to doing an SRS of just 10 people?