---
title: 'Chapter 1: Why Bar Graphs are Misleading'
description:
  'This chapter will teach you about why bar graphs are misleading.'
prev: null
next: /chapter2
type: chapter
id: 1
---

<exercise id="1" title="Introduction" type="slides">

<slides source="chapter1_01_introduction">
</slides>

</exercise>

<exercise id="2" title="Bar Graph Question 1">

<img src="https://raw.githubusercontent.com/dbturner/raisethebar/main/static/length.png" alt="bar graph of mean shell lengths with standard errors. The y-axis limits go from 0-80mm. The greatest means reach to about 75mm, while the smallest means are around 45mm." width="60%"/>

### What is the sample size for each group?

<choice>

<opt text="all groups have large (>30) sample size">
How can you tell what the sample size is from this graph?
</opt>

<opt text="all groups have small (<10) sample size">
How can you tell what the sample size is from this graph?
</opt>

<opt text="the number in each group is unclear, but they are all the same sample size">
How can you tell that the sample sizes are equal from this graph?
</opt>

<opt text="the number in each group is not clear from this graph" correct="true">
There is no way to tell from the graph given here what the sample size is for each group.
</opt>

</choice>
</exercise>

<exercise id="3" title="Bar Graph Question 2">

<img src="https://raw.githubusercontent.com/dbturner/raisethebar/main/static/length.png" alt="bar graph of mean shell lengths with standard errors. The y-axis limits go from 0-80mm. The greatest means reach to about 75mm, while the smallest means are around 45mm." width="60%"/>

### Mussels lengths in both locations in all four years display a normal distribution.

<choice>

<opt text="true, the data show a normal distribution">
How can you tell what the distribution of mussels lengths is from this graph?
</opt>

<opt text="false, the data show a non-normal distribution">
How can you tell what the distribution of mussels lengths is from this graph?
</opt>

<opt text="it is unclear what the distribution of the data is" correct="true">
There is no way to tell from the graph given here what the distribution is for each group.
</opt>

</choice>
</exercise>

<exercise id="4" title="Bar Graph Question 3">

<img src="https://raw.githubusercontent.com/dbturner/raisethebar/main/static/length.png" alt="bar graph of mean shell lengths with standard errors. The y-axis limits go from 0-80mm. The greatest means reach to about 75mm, while the smallest means are around 45mm." width="60%"/>

### What is the length of the largest mussel?

<choice>

<opt text="None of the groups have mussel shell lengths greater than 80mm">
How can you tell what the maximum mussel length is from this graph?
</opt>

<opt text="All of the groups have a maximum mussel shell length that is greater than 80mm">
How can you tell what the maximum mussel length is from this graph?
</opt>

<opt text="The largest mussel shell in all the groups is approximately 131 mm long">
How can you tell what the maximum mussel length is from this graph?
</opt>

<opt text="The largest mussel shell length in all the groups is approximately 79 mm long">
How can you tell what the maximum mussel length is from this graph?
</opt>

<opt text="It is unclear from this graph what the maximum mussel shell length is for each group" correct="true">
There is no way to tell from the graph given here what the maximum mussel length is.
</opt>

</choice>

</exercise>

<exercise id="5" title="Why Bar Graphs are Misleading" type="slides">

<slides source="chapter1_05_misleading">
</slides>

</exercise>

<exercise id="6" title="Dot Plot Question 1">

<img src="https://raw.githubusercontent.com/dbturner/raisethebar/main/static/dot2.png" alt="dot plot of individual mussel lengths jittered to show distribution of data and with median shown as a horizontal bar. Sample sizes from 29-219 shown. Points in each group show some clumpy clouds of points. Maximum values for all groups approach or exceed 100 mm." width="60%"/>

### What is the sample size for each group?

<choice>

<opt text="all groups have large (>30) sample size">
One group (mussels in the Manhan River in 2018) has only 29 samples
</opt>

<opt text="all groups have small (<10) sample size">
None of the groups are less than 10
</opt>

<opt text="the number in each group is unclear, but they are all the same sample size">
Sample sizes are shown and are not equal
</opt>

<opt text="the number in each group varies between 29-219 mussels" correct="true">
The sample size for each group (N) is given at the top of the graph. The sample size varies among rivers and years.
</opt>

</choice>
</exercise>

<exercise id="7" title="Dot Plot Question 2">

<img src="https://raw.githubusercontent.com/dbturner/raisethebar/main/static/dot2.png" alt="dot plot of individual mussel lengths jittered to show distribution of data and with median shown as a horizontal bar. Sample sizes from 29-219 shown. Points in each group show some clumpy clouds of points. Maximum values for all groups approach or exceed 100 mm." width="60%"/>

### Mussels lengths in both locations in all four years display a normal distribution.

<choice>

<opt text="true, the data show a normal distribution">
The jittered points do not show a normal distribution. Some are multimodal.
</opt>

<opt text="false, the data show a non-normal distribution" correct="true">
Some of the data is multimodal and the data are not all normally distributed.
</opt>

<opt text="it is unclear what the distribution of the data is">
Look at the distribution of the jittered points in each group - do they all look like a normal distribution?
</opt>

</choice>
</exercise>

<exercise id="8" title="Dot Plot Question 3">

<img src="https://raw.githubusercontent.com/dbturner/raisethebar/main/static/dot2.png" alt="dot plot of individual mussel lengths jittered to show distribution of data and with median shown as a horizontal bar. Sample sizes from 29-219 shown. Points in each group show some clumpy clouds of points. Maximum values for all groups approach or exceed 100 mm." width="60%"/>

### What is the length of the largest mussel?

<choice>

<opt text="None of the groups have mussel shell lengths greater than 80mm">
Can you see that many of the mussels clearly go above 80mm? Compare this to the bar graph where this is not so clear.
</opt>

<opt text="All of the groups have a maximum mussel shell length that is greater than 80mm" correct="true">
While it is hard to tell the precise values, you can see that the maximum mussel length reaches close to at least 100 mm for all the years in the Manahan River and the maximum value is well over 100 mm for all the mussles measured in the Mill Rivevr.
</opt>

<opt text="The largest mussel shell in all the groups is approximately 150 mm long">
The maximum mussel length for each location in each year varies, but none reach to 150 mm
</opt>

<opt text="The largest mussel shell length in all the groups is approximately 80 mm long">
The maximum mussel length for each location in each year varies
</opt>

<opt text="It is unclear from this graph what the maximum mussel shell length is for each group">
Unlike the bar graph where you could not tell what the maximum mussel length is for each group, this graph clearly shows the maximum because you can see all the points.
</opt>

</choice>

</exercise>