# 1.2 - Displaying quantitative data with graphs - PowerPoint PPT Presentation

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1.2 - Displaying quantitative data with graphs. (Histograms). Histograms. The most common graph of quantitative data. (not the most convenient) Classes: the intervals along the bottom axis. These need to be of equal width Frequency: the count of individuals of a class occurring

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1.2 - Displaying quantitative data with graphs

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(Histograms)

### Histograms

The most common graph of quantitative data.

(not the most convenient)

Classes: the intervals along the bottom axis.

These need to be of equal width

Frequency: the count of individuals of a class occurring

Relative frequency: the percent of the individuals in a class

(this is more useful, especially when you are comparing two sets of data with an unequal total of individuals)

• The following table represents the battings averages for the 25 Cincinnati Reds who have an at bat this time in the 2013 season.

### Door Side

• The following table represents the battings averages for the 29 Cincinnati Reds who have an at bat this time in the 2014 season.

### Steps for constructing a histogram

1st - divide the range of data into class of equal width.

2nd - find the count and percent of individuals in each class.

3rd - label and scale your axes

### 1st step

What is the range of our data?

What would be a good class size to choose?

What are the classes?

### 2nd Step

Fill in a frequency table and a relative frequency table.

• 2013

• 2014

• Relative Frequency

• Relative Frequency

### 3rd step

• Batting Average

• Batting Average

• The histogram shows that the batting ranged from __________

• The data appears to be _______ with a peak of _____ .

• The center of the data occurs around ______

### Describe the data of the batting average for YOUR year only!

• The _____ appear to be any outliers.

### Now let’s COMPARE the batting averages from 2013 and 2014

• www.whfreeman.com/tps4e

### How does class size effect the shape of the histogram?

• 2. Don’t use the counts or percents as the data. Use the data to find the counts and percents for your graph.

• 3. Use percents instead of counts when comparing distributions with different numbers of observations.