What other variablesare often used in statistics?
When an experiment is conducted, variables manipulated by the experimenter are
called independent variables(also independent factors), while others measured from
the subjects are called dependent variables (also dependent measures). For example,
consider a hypothetical experiment on the effect of lack of sleep on reaction time:
Subjects either stayed awake, slept for 2 hours for every 24, 5 hours for every 24, or 8
hours for every 24; they then had their reaction times tested. The independent vari-
ables would be the hours slept by each person and the dependent variables would be
the reaction time.
Some variables can be measured on a continuous scale—a continuous variable
being one that, within the limits the variable ranges, can take on any value possible.
For example, we can make the time to eat a lunch at a certain restaurant be the con-
tinuous variable because it can take any number of minutes or hours to finish the
meal. But other variables can only take on a limited number of values—or dependent
variables. For example, if the variables were a test score from 1 to 10, then only those
10 possible values would be allowed; these are called discrete variables.
What are the measures of central tendency?
The measures of central tendency are statistics that describe the grouping of values in
a data set around a common value that in some way represents a typical member. They
are broken down into four types: median, mode, average (also called the arithmetic
mean), and the geometric mean.
What are the arithmetic meanand geometric mean?
The average, in general, means the average value of a group of numerical observa-
tions—or the statistical measure of the arithmetic mean (or just the mean). On a scale
of measurement, it is usually the place in which the population is centered. Numeri-
cally, it equals the sum of the scores divided by the number of scores. For example, the
sum of 3, 7, 10, 15, and 25 is 60; thus, the mean is 60 divided by 5, or 12. The geomet-
ric mean is another type of mean: For two quantities, it is the square root of the quan-
tities’ product; the notation is for nquantities, and the geometric mean is the nth root
of their product.
What are medianand mode?
The median is considered half the sum of the two numbers nearest the middle. In
other words, in an ordered data set, the median is the value at the halfway point, above
and below which lie an equal number of data values. (But note: There is an actual mid-
dle number for a set with an odd number of members, but no middle number for an
even number of members.) 259