How to define experimental units
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AP Statistics › How to define experimental units
When designing an experiment, what is the purpose of blocking?
To separate a particular sample into groups previously known to be similar in some way that are expected to affect response to treatments
To increase the number of experimental units
To use chance to randomly assign experimental units to treatment groups (or vice versa)
To hold an extraneous variable constant
None of the other answers
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.
Of the following examples, which best describes quantitative data?
Temperature measurements of water in degrees Fahrenheit.
A student's least favorite sport.
College grade level-freshman, sophomore, junior, or senior.
A child's gender.
The softness of a chair.
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.
Which of the following is an example of qualitative data?
The gender of a high school student
The speed at which a car is traveling
The temperature of a glass of water
The amount of carbon monoxide emissions in the air
The average SAT score of students at a particular high school
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.