What is the difference between descriptiveand inferential statistics?
Descriptive statistics is a way to describe the characteristics of a given population by mea-
suring each of its items, then taking a summary of the measurements in various ways.
Inferential statistics, as the term implies, makes educated inferences (guesses) about the
characteristics of a population by taking and analyzing data from a random sample.What are quantitativeand qualitative variablesas used in statistics?
Variables are values used to come to conclusions in a statistical study. There are two
main categories: quantitativeand qualitativevariables. Quantitative variables can be
divided into three types. Ordinal variables are measured with an ordinal scale, in
which higher numbers represent higher values, even though the intervals between
numbers are not necessarily equal. For example, on a five-point rating scale measur-
ing attitudes toward cutting back on air pollution, the difference between a rating of 2
and 3 may not be the same as the difference between a rating of 4 and 5. Interval vari-
ables are measured with an interval scale, in which one unit on the scale represents
the same magnitude of the characteristic being measured across the whole range of
the scale. For example, the Fahrenheit scale for temperature is an interval scale, in
which equal differences on this scale represent equal differences in temperature, but a
temperature of 30 degrees is not twice as warm as one of 15 degrees. The third type is
the ratio scale variable. This is a scale similar to the interval scale, but with true zero
points. For example, the Kelvin temperature scale is a ratio scale because it has an
absolute zero. Thus, a temperature of 300 Kelvin is twice as high as a temperature of
150 Kelvin.Qualitative variablesare measured on a nominal scale, or a measurement that has
assigned items to groups or categories. With these variables, there is no quantitative
information and no ordering of the items is conveyed—it is qualitative rather than
258 quantitative. Religious preference, race, and gender are all examples of nominal scales.
What type of sampling technique is often used in opinion polling?
W
e all know about opinion polls, especially during a major election. The sta-
tistical sampling method of most polling places is called quota sampling,a
technique in which interviewers are given a quota of specific types of subjects to
poll. For example, the sampling may involve asking 10 adult men, 10 adult
women (both groups over 20 years of age) and 10 teenage (18 to 19 years old)
voters for their opinion on the presidential election. But as we all know, these
types of polls are not as accurate as they should be, mainly because the sample is
not random.