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Graphs Line Bar Pie chart …
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USING GRAPHING SKILLS
Axis While drawing graphs, we have two
axis.
X-axis: for consistent variables
Y-axis: for other variable
Graphs Line
Bar
Pie chart
…
Line graph It best shows the relationship between
two variables
Bar graph:Uses column to compare variables.
STATISTICAL ANALYSIS
The science of data
Statistics in Science Biological systems are subject to
environmental effects and genetic variation, therefore, they show differences from each other.
Similarities or differences between the organisms can be shown by using statistics.
How can we show similarities and differences?
egg radius of population x & y
x y
0
2
4
6
8
10
populations
radi
us (m
m)
What do error bars suggest?If the bars show extensive overlap, it is likely that there is not a significant difference between those values.
For this graph write down the systems showing overlap with rating zone.
How can we show similarities and differences?
egg radius of population x & y
x y
0
2
4
6
8
10
populations
radi
us (m
m)
Drawing error bars A way to draw an error bar is to use the
mean as the central point, and to use standard deviation as the end points of the error bar.
How do we calculate “Mean” & “Standard Deviation” ?
Firstly, some information…
•Mean: Average, central tendency of the data Also
• Median• Mode• Range
•Standard Deviation: spread of data around the mean.
How do we calculate “Mean” & “Standard Deviation” ?
EXAMPLE:How can leaf lengths be displayed graphically?
Simply measure the lengths of each and plot how many are of each length
If smoothed, the histogram data assumes this shape
This Shape? Is a classic bell-shaped curve, a Normal
Distribution curve.
The standard deviation is a statistic that tells you how tightly all the various examples are clustered around the mean in a set of data
A typical standard distribution curve
According to this curve: One standard deviation away from the
mean in either direction on the horizontal axis (the red area on the preceding graph) accounts for somewhere around 68 percent of the data in this group.
Two standard deviations away from the mean (the red and green areas) account for roughly 95 percent of the data.
Three Standard Deviations? three standard deviations (the red, green
and blue areas) account for about 99 percent of the data
-3sd -2sd +/-1sd 2sd +3sd
How is Standard Deviation calculated?
With this formula!
AGHHH! HOCAM
DO I NEED TO KNOW THIS FOR THE TEST?????
Not the formula! This can be calculated on a scientific calculator OR…. In Microsoft Excel, type the following code into the
cell where you want the Standard Deviation result, using the "unbiased," or "n-1" method: =STDEV(A1:A30) (substitute the cell name of the first value in your dataset for A1, and the cell name of the last value for A30.)
OR….Try this! http://www.pages.drexel.edu/~jdf37/mean.htm
Comparison of two sample means and St. deviations
http://click4biology.info/c4b/1/stat1.htm
A sample with a small standard deviation suggest narrow variation but a second sample with a larger standard deviation suggests wider variation.