Microsoft Office Tutorials and References
In Depth Information
be a sample, then the division is by the number of observations minus 1. The
standard deviation formula in Excel for observations that are assumed to be a
sample ( unbiased version )is STDEV(number1, number2
) . In the case where
we assume our observations represent a population (all possible observations),
the formula is STDEVP(number1, number2,
5. A range is a simple, but useful, measure of variation which is calculated as the
high observation value minus the low.
6. A population is the set of all possible observations of interest.
7. The median is the data point in the middle of the distribution of all data points.
There are as many values below as above the median.
8. The mode is the most often occurring value in the data observations.
9. The standard error is the sample standard deviation divided by the square root
of the number of data observations.
10. Sample variance is the square of the sample standard deviation of the data
11. Kurtosis (peakedness) and skewness (asymmetry) are measures related to the
shape of a data organized into a frequency distribution.
In most cases, it is likely we are not interested in viewing our time series data
as a distribution of points, since frequency distributions generally ignore the time
element of a data point. We might expect variation and be interested in examining
it, but usually with a speciﬁc association to time. A frequency distribution does not
provide this time association for data observations.
Let us examine the data sets by employing descriptive statistics for each type of
data: time series and cross-sectional. We will see in the next section that some of
Excel’s descriptive statistics are more appropriate for some types of data than for
3.4.3 Analysis of Time Series Data—Descriptive Statistics
Consider the time series data for our Sales example. We will perform a very
simple type of analysis that generally describes the sales data for each product—
Descriptive Statistics . First, we locate our data in columnar form on a worksheet. To
perform the analysis, we select the Data Analysis tool from the Analysis group in the
Data ribbon. Next we select the Descriptive Statistics tool as shown in Exhibit 3.11.
A dialogue box will appear that asks you to identify the input range containing the
data. You must also provide some choices regarding the output location of the anal-
ysis and the types of output you desire (check the summary statistics box). In our
example, we select data for product A. See Exhibit 3.12. We can also select all of
the products (A–E) and perform the same analysis. Excel will automatically assume
that each column represents data for a different product. The output of the analysis
for product A is shown in Exhibit 3.13.