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2.2 Graphs and Tables for Quantitative DataObjectives:By the end of this section, I will beable to…

1) Construct and interpret a frequency distribution and a relative frequency distribution for quantitative data.

2) Use histograms and frequency polygons to summarize quantitative data.

Section 2.2

Graphs and Tables for QUANTITATIVE Data

We need DATA• What are the ages of your

siblings?

SORT DATA

• First thing we want to do is plug the data into our calculators (STAT – EDIT – LIST1)

• Then Sort your data (STAT – SORTA() – 2nd 1 – ENTER)

Frequency Distribution

• Is a table that organizes data.

Class # Interval Class Midpoint

Freq. Relative Freq

Frequency Distribution

Step 1: Determine how many classes

Step 2: Determine the CLASS WIDTH

1) find the RANGE of data

2) Divide RANGE by # of classes

3) Round the answer

Step 3: Determine the upper and lower class limits

Frequency Distribution

• Fill out the Table

Class # Interval Class Midpoint

Freq. Relative Freq

Histogram• uses INTERVALS• Has TOUCHING BARS• Its NOT a bar graph

Histogram• Create a histogram by hand • Label all your axes• Make the bars touching!• x axis = ages of siblings• y axis = frequency

On the calculator

• Now let’s graph a histogram on the calculator

Distribution Shape

We need to analyze the shape of the graphs.

There are two types of shapes.• Symmetric• Skewed

Distribution Shape• Symmetric: if there is a line that splits the graph in

half so that one side is a mirror image of the other• The Bell Shaped Curve is a great example of a

symmetric graph.

Distribution Shape

• Skewness: when a graph has a longer tail on one side– Left skewed vs. right skewed

Frequency Polygon• Uses dots to plot the CLASS MIDPOINTS• It is NOT a line graph • Can be found in the financial section of

newspapers/internet

Frequency Polygon• Create a frequency polygon by hand• Label all your axes• Connect your dots!• x axis = ages of siblings• y axis = frequency