08-02-2013, 11:00 AM
Descriptive Statistics: Numerical Methods
1Descriptive Statistics.ppt (Size: 801.5 KB / Downloads: 33)
Example: Apartment Rents
Given below is a sample of monthly rent values ($)
for one-bedroom apartments. The data is a sample of 70
apartments in a particular city. The data are presented
in ascending order.
Median
The median is the measure of location most often reported for annual income and property value data.
A few extremely large incomes or property values can inflate the mean.
The median of a data set is the value in the middle when the data items are arranged in ascending order.
For an odd number of observations, the median is the middle value.
For an even number of observations, the median is the average of the two middle values.
Mode
The mode of a data set is the value that occurs with greatest frequency.
The greatest frequency can occur at two or more different values.
If the data have exactly two modes, the data are bimodal.
If the data have more than two modes, the data are multimodal.
Percentiles
A percentile provides information about how the data are spread over the interval from the smallest value to the largest value.
Admission test scores for colleges and universities are frequently reported in terms of percentiles.
Measures of Variability
It is often desirable to consider measures of variability (dispersion), as well as measures of location.
For example, in choosing supplier A or supplier B we might consider not only the average delivery time for each, but also the variability in delivery time for each.