AP Statistics : How to define experimental units

Study concepts, example questions & explanations for AP Statistics

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Example Questions

Example Question #1 : How To Conduct An Experiment

Of the following examples, which best describes quantitative data?

Possible Answers:

Temperature measurements of water in degrees Fahrenheit.

The softness of a chair.

College grade level-freshman, sophomore, junior, or senior.

A student's least favorite sport.

A child's gender.

Correct answer:

Temperature measurements of water in degrees Fahrenheit.

Explanation:

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.

Example Question #3 : How To Conduct An Experiment

When designing an experiment, what is the purpose of blocking?

Possible Answers:

To increase the number of experimental units

To use chance to randomly assign experimental units to treatment groups (or vice versa)

To separate a particular sample into groups previously known to be similar in some way that are expected to affect response to treatments

To hold an extraneous variable constant

None of the other answers

Correct answer:

To separate a particular sample into groups previously known to be similar in some way that are expected to affect response to treatments

Explanation:

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.

Example Question #1 : How To Define Experimental Units

Which of the following is an example of qualitative data? 

Possible Answers:

The temperature of a glass of water

The speed at which a car is traveling

The gender of a high school student

The amount of carbon monoxide emissions in the air

The average SAT score of students at a particular high school 

Correct answer:

The gender of a high school student

Explanation:

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.

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