What Does the Graph Say?
Directions:
● Read the article in this link about error bars: https://www.biologyforlife.com/interpreting-error-bars.html
●
Look over these example graphs. Under each graph write a detailed explanation about what the graph
is telling you, what conclusions can you draw from the data presented?
Graph 1:
The Mean Salary for Assistant Professor,
AssociateProfessor and Lead Professors at
US Universities (Male and Female Comparison)
Graph 2:
Comparison of Shady & Sunny Ivy Plant
Leaf Width
Graph 1:
Graph 2:
The graph suggests that female assistant professors, associate
The graph states that ivy plants in shade have a higher mean
professors, and lead professors at US universities have a lower
leaf width than their sunny counterparts. The difference is on
mean salary than their male coworkers. While the male group
average 1.5 centimeters, with very small error bars on both data
has small error bars, the standard deviation for females is
sets that do not overlap. The difference in leaf width is likely
much larger and tends to overlap with the males' error bars.
significant, but a statistical test would have to be done for
This is an indication that a statistical test should be done to
confirmation.
confirm differences between salaries.
Graph 3: The Amount of Prolactin in the
Blood Plasma after Exercise
And Rest
Graph 4: Heart Rate for 100 Test Subjects
Completing Jumping Jacks
* Researchers conducted a study to investigate the
Effect of exercise on the release of prolactin into the blood.
Concentrations of prolactin in eight adult males before (T=0)
and after one hour (T=1hour) of vigorous exercise. As a control,
the same 8 men were tested 1 week later at the same time
of the day but did not exercise.
Graph 3:
Graph 4:
The graph shows that without exercise, male adults maintain a
There is a clear, nearly linear increase in mean heart rate for
very similar amount of prolactin in blood plasma over time. The
every 5 jumping jacks performed. The biggest increases are seen
difference from hour 0 to hour 1 is on average 0.5 mmol/L, with
going from 0 to 5 and 5 to 10, but it is also these points which
large error bars overlapping each other, suggesting statistical
have the largest error bars. This indicates that subjects generally
insignificance. With exercise, however, a more pronounced
have different initial responses to exercise, but these differences
difference is seen, with subjects having an average of 1 mmol/L
shrink beyond 10 jumping jacks. The data appears to be
more prolactin in their blood plasma after exercise.
statistically significant, but a statistical test must be performed.
Unfortunately, there is a very large error bar on hour 0 that
completely overlaps with the error bar on hour 1. In both cases,
with or without exercise, the prolactin levels need to be
statistically tested to confirm any significant difference.