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

observations.

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

others.

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.

Search JabSto ::

Custom Search