Statistics
Parameter
is a number that describes the population
A member of Congress wishes to determine her constituency's opinion regarding estate taxes. She divides her constituency into three income classes: low-income households, middle-income households, and upper-income households. She then takes a simple random sample of households from each income class. What sampling method was used?
Stratified
To estimate the percentage of defects in a recent manufacturing batch, a quality-control manager at Intel selects every 8th chip that comes off the assembly line starting with the 3rd until she obtains a sample of 140 chips. What sampling method was used?
Systematic
A radio station asks its listeners to call in their opinions regarding the use of U.S. forces in peacekeeping missions. What sampling method was used?
Volunteer
What can we say about the relationship between the correlation r and the slope b of the least-squares line for the same set of data?
r and b have the same sign (+ or -).
To determine the prevalence of human growth hormone (HGH) use among high school varsity baseball players, the State Athletic Commission randomly selects 50 high schools. All members of the selected schools' varsity baseball teams are tested for HGH. What sampling method was used?
Cluster
Suppose that the city has 10 hospitals. Choose one of the 10 hospitals at random and interview all the nurses in that hospital regarding their job satisfaction. What kind of sampling distribution is this?
Cluster Sampling
The research foundation identifies 5 large companies that represent a broad cross-section of patients,chooses 2 of the 5 at random, and gains access to the claims of all the companies' patients. What kind of sampling distribution is this?
Cluster Sampling
7th grade students are randomly divided into two groups. One group is taught math using traditional techniques; the other is taught math using a reform method. After 1 year, each group is given an achievement test to compare proficiency. What kind of study is this?
Experiment
While shopping, 200 people are asked to perform a taste test in which they drink from two randomly placed, unmarked cups. They are then asked which they prefer. What kind of study is this?
Experiment
In order to obtain a sample of undergraduate students in the United States, a simple random sample of 10 states is selected. From each of the selected states, 10 colleges or universities are chosen at random. Finally, from each of these 100 colleges or universities, a simple random sample of 20 undergraduate students is selected. Thus, the final sample consists of 2,000 undergraduates. What kind of sampling distribution is this?
Multistage Sampling.
A poll is conducted in which 500 people are asked whom they plan to vote for in the upcoming election. What kind of study is this?
Observational
Conservation agents netted 250 large-mouth bass in a lake and determined how many were carrying parasites. What kind of study is this?
Observational
Following the 2010 national midterm election , 18% of the governors of the 50 United States were female. Determine whether 18% is a parameter or a statistic.
Parameter
Ty Cobb is one of major league baseball's greatest hitters of all time, with a career betting average of 0.366. Determine whether 0.366 is a parameter or a statistic.
Parameter
24hr Fitness wants to administer a satisfaction survey to its current members. Using its membership roster, the club randomly selects 40 club members and asks them about their level of satisfaction with the club. What sampling method was used?
SRS
Voters are selected at random from an alphabetical list of all registered voters. What kind of sampling distribution is this?
Simple Random Sampling
A study of 6076 adults in public restrooms in (Atlanta, Chicago, New York city, and San Francisco) found that 23% did not wash their hands before exiting. Determine whether 23% is a parameter or a statistic.
Statistic
Interviews of 100 adults 18 years of age or older, conducted nationwide, found that 44% could state the minimum age requirement for the office of U.S. president. Determine whether 44% is a parameter or a statistic.
Statistic
Choose a random sample of 50 nurses from each of the 10 hospitals and interview these 50 * 10 = 500 regarding their job satisfaction. What kind of sampling distribution is this?
Stratified Sampling
From each region, 5 representative counties are selected. (In total, all the claims originating from 35 counties are examined.)What kind of sampling distribution is this?
Stratified Sampling
The 2 companies' claims are classified (depending on their origin) according to 7 geographical regions,and within each region, the sampling continues.What kind of sampling distribution is this?
Stratified Sampling
Within each county (and for each company), claims of 25 male and 25 female patients are randomly selected.What kind of sampling distribution is this?
Stratified Sampling
A health educator wanted to study the sleeping habits of the undergraduate students in her university. For her study, the researcher chose a simple random sample of size 150 from each of the classes (150 freshmen, 150 sophomores, 150 juniors, and 150 seniors), for a total of 600 sampled students. What kind of sampling distribution is this?
Stratified Sampling?
Stratified Sampling
Stratified sampling is used when our population is naturally divided into sub-populations, which we call stratum (plural: strata). For example, all the students in a certain college are divided by gender or by year in college; all the registered voters in a certain city are divided by race. In stratified sampling, we choose a simple random sample from each stratum, and our sample consists of all these simple random samples put together. For example, in order to get a random sample of high-school seniors from a certain city, we choose a random sample of 25 seniors from each of the high schools in that city. Our sample consists of all these samples put together.
A correlation of r = .85 is found between weekly sales of firewood and cough drops over a 1-year period. Which of the following is true?
Temperature is a possible lurking variable that is "behind" this relationship.
A study was done on the timeliness of flights (on-time vs. delayed) of two major airlines: StatsAir and AirMedian. Data were collected over a period of time from five major cities and it was found that StatsAir does better overall (i.e., has a smaller percentage of delayed flights). However, in each of the five cities separately, AirMedian does better.
This is an example of Simpson's Paradox. "City" is a lurking variable in this example.
Cluster Sampling
This sampling technique is used when our population is naturally divided into groups (which we call clusters). For example, all the students in a university are divided into majors; all the nurses in a certain city are divided into hospitals; all registered voters are divided into precincts (election districts). In cluster sampling, we take a random sample of clusters, and use all the individuals within the selected clusters as our sample. For example, in order to get a sample of high-school seniors from a certain city, you choose 3 high schools at random from among all the high schools in that city, and use all the high school seniors in the three selected high schools as your sample.
Statistic
is a number that is computed from the sample.
Simple Random Sampling
is, as the name suggests, the simplest probability sampling plan. It is equivalent to "selecting names out of a hat." Each individual as the same chance of being selected.
In order to study whether IQ level is related to birth order, data were collected from a sample of 540 students on their birth order (Oldest/In Between/Youngest) and their score on an IQ test. The data collected in this study would be best displayed using:
side-by-side boxplots
Suppose that the correlation r between two quantitative variables was found to be r = 0. This means that:
there is no linear relationship between the two variables.
