Data Collection - AP Statistics

The control group receives no treatment.

The experimental group receives the treatment of the independent variable.

Because the flowers getting no dye do not receive the treatment, it is the control group.

The control group receives no treatment.

The experimental group receives the treatment of the independent variable.

Because the sunflowers getting no fertilizer do not receive the treatment, it is the control group.

Quantitative data describes a certain type of information that can be counted or expressed numerically and can be used in meaningful computations. Quantitative data is different from qualitative data, which is primarily involved in describing things in terms of categorizations or specific qualities. Looking at the answer choices, it is clear that measuring the temperature of water in degrees Fahrenheit is a numerical piece of information, and is thus quantitative.

The purpose of blocking, by definition, is to separate a particular sample into groups previously known to be similar in some way that are expected to affect response to treatments. The other choices pertain to control (keeping an extraneous variable constant), randomization (using random chance to assign experimental units to treatments), and replication (increasing the number of experimental units to reduce chance variation) in an experiment.

The only example of qualitative data here is the gender of a high school student (i.e. male or female). This cannot be quantified, unlike the other answer choices which all have numbers, quantities, and amounts associated with them.

The only random procedure here is the coin flip. In expectation, the coin flip ensures that no background variables influence treatment assignment whereas the other examples either have nothing to do with random assignment (e.g. nationally representative sample) or completely contradict the purpose of random assignment (e.g. assigning the treatment based on who needs it the most).

Since Shawn would like to know the most popular television channel in his town, he must include all residents of the town in his target population. The sample must come from the directory and each person in the directory should have an equal chance of being selected. The incorrect options are too narrowly focused and are not representative of the town.

Taking a random sample is the only data-collecting method that ensures that every set of individuals has an equal chance of being selected for the sample and does not introduce any significant bias. Taking either a voluntary response sample or a convenience sample does not ensure these important aspects, as there is some unwanted selectivity involved in the data being collected. Taking a census is inferior to taking a sample of any sort, as it is both costly and time-consuming.

A continuous variable can take on an infinite continuum of possible real number values. Weight and the amount of time to read a book are continuous because it is impossible to write down all the distinct potential values.

A binomial model counts the number of successes out of a specific number of attempts at a task when each attempt has a constant probability of success. The correct choice is the one that specifies the number of attempts.

The company wants a survey on what consumers want. That means they are interested in all possible consumers. The other groups are too specific.

Since your teacher has asked that you determine the most popular cereal brand at your high school, the survey population should be limited to only your high school. Other students' preferences of cereal brands around the nation will have no impact on the survey results.

Additionally, surveying only students in your AP Statistics class or only students in a particular grade level would not be representative of all students in your high school. Therefore, the correct survey population is all students in your high school.

The best answer is the choice that reduces the amount of bias in the selection of survey participants. Surveying local residents at a grocery store, neighborhood park, or shopping mall would introduce selection bias into the survey since every member of the target population does not have an equal chance of being selected. Using the random number generator, every single person in the neighborhood has an equal chance of being selected to take the survey.

Random sampling is a method in which every individual has an equal opportunity of being randomly chosen to participate in a study.

Cluster random sampling entails choosing from pre-formed "clusters"-- such as schools or hospitals-- and randomly selecting one of the clusters.

In order for cluster sampling to be present, the entire population must be divided into homogeneous groups (known as clusters). For sampling purposes in this problem, clusters must be chosen as a simple random sample. There is only one answer choice that fits this pattern.

A simple random sample is obtained by randomly selecting individuals from a target population. Each individual in the target population (i.e. all students at the high school) should have an equal chance of being selected. Only one answer choice gives each high school student an equal chance of being selected: choosing students at random from the high school.

Many people are reluctant to be honest about their bad behaviors, especially if they don't believe the survey is confidential. This will cause participants to be more likely to respond with whatever is more socially acceptable.

Stratified Sampling is the method of randomly selecting subjects from various stratum, or subsets of the population. In this case, there were 4 stratum from which participants were randomly selected.

In order for there to be a stratified random sample, the target population must be split into different groups (i.e. grade levels). The sample population must be selected at random from each of these groups (i.e. choosing students from each of four different grade levels or groups). The other examples, although random, are not specifically stratified in their sampling methodology.

Because the survey is being conducted on drivers at a gas station, people/households who do not own a motor vehicle will not be included in the survey.