# Simple Descriptive Statistics

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```GEOG 090 – Spring 2005
Assignment #2 – Simple Descriptive Statistics
Due: Thursday, February 17, 2005 at the beginning of class
1. Follow the instructions for Question 1 on page 16 of Rogerson, using the linked data
set, with the following changes:
(a)
and every step (i.e. you may use Excel like a calculator, but you still must show
your work). DO NOT calculate the interquartile range, but compute all the
other requested descriptive statistics (mean, median, range, standard deviation,
variance, skewness, and kurtosis) for the first 19 values. DO NOT construct
any plots.
(b)
You may use Excel’s built-in functions to calculate the mean, median, range,
standard deviation, and variance for the 236 observations. A particularly
convenient way to do this uses the Data Analysis ToolPak’s Descriptive
Statistics option. DO NOT use the SKEW() and KURT() functions for
skewness and kurtosis in Excel (or the results for those values from the
Descriptive Statistics output) since they are defined differently from those that
we are using. Instead, I will provide the skewness and kurtosis values for the
full data set:
Skewness = 0.739
Kurtosis = 2.417
Note that with a dataset of this size the skewness and kurtosis calculated using
our formula starts to approach that produced by Excel (Sk=0.749, Ku=2.542).
(c)
Answer this part of the question as specified in the text.
2. Follow the instructions for Question 2 on page 16 of Rogerson, as specified in the text
and ALSO calculate the coefficient of variation.
3. Follow the instructions for Question 3 on pages 39-40 of Rogerson, as specified in the
text. There are 7 sums to be calculated; be sure to identify each sum appropriately
(i.e. either label them parts (a) through (g), or write out the sigma notation for each of
them first {e.g.  xi = etc.} so I know which sum is which).
4. Using the linked data sets for sampling locations in Pond Branch and sampling
locations in Glyndon:
(a)
Calculate the mean centers of the sampling locations in each catchment (i.e.
report the result as an (x,y) coordinate pair that is the mean center of each set of
sampling locations).
(b)
Calculate the standard distance of the sampling locations in each catchment (i.e.
report the standard distance in meters, the same units that the coordinates have).
(c)
In which catchment are the sampling points more dispersed (i.e. further apart
from one another)?
Format for answering questions in GEOG 090
1.
2.
3.
4.
5.
6.
7.
Show all of your work in a neat, organized fashion.
If numbers are to be plugged into a formula, write out the formula first.
Provide the units of a final answer if applicable.
Final numerical answers should be circled for easy identification
Graphs should be large enough to discern - make liberal use of graph paper.
Graphs, tables should have a title and legend (if there is more than one variable
portrayed).
Axes on graphs should be labeled with the variable name and the units.
2
```