Suppose gathering all this data were very expensive. An alternative approach would be to
take a sample from this population. Assume the observations 37, 58, 35, 54 were chosen as a
sample from the population above.
a. Compute the mean. _______________
b. Is this a sample or population mean? _______________
Compute the mean for the following samples.
Sample 1: 22, 29, 22, 7, 34. _________________
Sample 2: 22, 29, 22, 7, 10,000. ________________
The second measure of central tendency is called the MEDIAN. The median is a positional
average. It is determined by arranging the data in ascending or descending order and locating
the middle value.
If there is an even number of observations in our data, we find the median by taking the mean
of the MIDDLE two values. If there is an odd number of observations, there will always be one
value in the data set that is the median.
For example, suppose we have the following nine observations: 1, 22, 29, 23, 7, 34, 14, 17, 31.
We would find the median by arranging the data in ascending (or descending) order and selecting
the middle value. Putting the values in ascending order gives: 1, 7, 14, 17, 22, 23, 29, 31, 34. The
median or middle value in this ordered list is 22. There are four values larger than 22 and four
values smaller than 22. If we arrange the data in descending order, the result would be the same.
What is the median of the following eight observations:
8, 24, 28, 19, 7, 31, 2, 22 ________________