1. Histogram
A frequency plot that shows the number of times a response or range of responses occurred in a data set.

2. It can only be used to show continuous data
What is a histogram?
A histogram is like a bar chart, but there are some important differences.
It can only be used to show continuous data
The bars on a histogram touch. The bars found on a bar graph do not touch.
It can only be used to show numerical data
The data is always grouped.

3. Histogram: Pros and Cons
Advantages:
Visually strong
Good for determining the shape of the data
Disadvantages:
Cannot read exact values because data is grouped into categories
More difficult to compare two data sets

4. How do you make a histogram?
Create a frequency table Count how many occurrences in the data
Be sure to create equal intervals
Label the x and y axis
Choose a scale to label
X and Y axis do not need to have the same scale
Draw a bar for each interval.
The height of the bar is the frequency for that interval.
Bars must touch but not overlap.

5. Let’s try!
A study collected the number of hours children watch TV. The collected the following number of hours: 8, 7, 5, 4, 9, 6, 3, 1, 7, 5, 4, 2, 3, 5, 2, 4, 3, 5, 7, 3, 6, 5, 3, 7, 2, 9, 6, 7, 8, 5, 4, 7, 3, 9, 4, 7, 3, 1, 2, 8, 5, 3, 7, 9, 5 1 6 2 7 3 8 4 9 5

6. Create the frequency table
Number of hours of TV
III 6 II 1
IIII IIII 7
IIII 2 8
IIII IIII 3 9
IIII I 4
IIII III 5
Frequency
Number of hours of TV 14
1-3 16
4-6 15
7-9

7. Label x and y axis (Choose your scale!) Draw the bars

8. How To Compare Distributions
Analyzing Histograms and Dot Plots

9. Analyzing Histograms
When you compare two or more data sets, focus on the following four features:
Center
Spread
Shape
Unusual Features

10. Analyzing Histograms and Dot Plots
Center (It is the MEDIAN)!
EXAMPLE

11. To Find the Center:
List out the numbers in order, smallest to largest, then find the median.
6,6,6,7,8,8,8,9,10,10,10,10,10,11,12
Center

12. Your Turn!

13. Analyzing Histograms and Dot Plots
Spread (RANGE)
Highest – Lowest = Range
Less Spread 4
EXAMPLES
More Spread 8

14. You Try!

16. Analyzing Histograms and Dot Plots
Shape The shape of a distribution is described by symmetry, amount of skew, number of peaks, etc.
Skewed Left
EXAMPLES
Symmetric, Unimodal
Skewed Right

17. 3 Overall Shapes: Normal/Symmetrical: Skewed left: Skewed right:
The shape is symmetrical around the middle.
Skewed left:
Most of the data is to the right, with a long tail to the left.
Skewed right:
Most of the data is to the left, with a long tail to the right.

18. You Try!

20. Analyzing Histograms Unusual Features Unusual features refer to
gaps: areas of the distribution where there are no observations and
Outliers: a data point that stands out from the rest. (1.5 times the IQR)
EXAMPLES
Gap
Outlier

21. You Try!

23. Graphical Displays for Data Homework
Classwork/HOMEWORK
Graphical Displays for Data Homework