Chapter 4
Obtaining Data
Section 4.1
1.
Operational definitions are used to define measurement procedures.
Benchmarks
are objects or procedures used to compare two or more products or processes.
2.
There would be many correct answers.
Here is one of them.
Numerous factors affect the fuel efficiency of a car.
These include the size and
weight of the car, driving style, road conditions, speed, type of gasoline, etc.
To simplify the problem, consider the task of determining the highway fuel
efficiency of just one make/year of car, a 1999 Ford Mustang.
Suppose you select 10 1999 Ford Mustang cars with similar options.
Each car is
inspected to ensure it is in good mechanical order.
The tire pressure is checked to
ensure it is at the recommended level.
The oil is changed and 10.0 gallons of
gasoline (with an octane rating of 87) is filled into each vehicle.
A test section of a highway in the vicinity of, say, San Angelo, Texas is selected.
A
test date during which time the weather is clear and the temperature remains
between 70 and 75 degrees Fahrenheit is selected.
Each of 10 test drivers is
employed to enter the highway, accelerate to 55 mph, and then drive their vehicles
(using standard rules of the highway) while maintaining 55 mph speed until such
time as the vehicle runs out of gasoline.
Upon completion of the trial, the distance each car traveled is recorded to the
nearest one tenth of a mile.
Then the fuel efficiency for each car is computed by
taking the distance traveled divided by 10.0 gallons, producing a fuel efficiency
value in miles/gallon.
Finally, the 10 cars’ miles/gallon fuel efficiency values are
averaged together and reported as the average highway fuel efficiency of a 1999
Ford Mustang under test conditions.
4  1
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Chapter 4
3.
For example, you might use a definition such as:
Temperature at 2:00 pm in a
fixed, unshaded area on top of City Hall
.
4.
The published reference would more properly be considered a benchmark, since a
benchmark is a welldefined object whose characteristics are already explicitly
known, as are the first 200 digits of the number
π
.
Section 4.2
5.
An obvious method would be:
Obtain an exact count of the number N of words in
the dictionary.
Use a random number generator (e.g., in Excel or a statistical
software package) to select a random sample of n integers from the numbers 1, 2, 3,
..., N
.
Although this sounds simple, finding N is usually not easy.
For example,
should you count singular and plural forms of a word as being the same or different
words?
Some operational definition will have to be created so that you know
exactly what words to count when finding N, and even after doing so, finding N will
be a huge task so this is generally not a practical method.
There are many methods that may sound good, but do not actually produce random
samples.
For instance, one such method is:
Pick a page at random, then pick a
column at random (assuming there are 2 columns per page), then pick a line at
random from the column, then use the word (in bold) that is described by that line
.
This is the end of the preview.
Sign up
to
access the rest of the document.
 Fall '08
 Hooper
 Statistics, researcher, Fuel efficiency

Click to edit the document details