Histograms I can display numerical data with a histogram.

A histogram is a graphical display where the data is grouped by range into

classes or bins, and plotted as bars. It is plotted with both a horizontal

and a vertical axis..

Vocabulary

The number of observations is

the number or pieces of data collected in the

sample.

The spread of the data is the range of the data

points.

The attribute is the specific

characteristic or feature of the graph. In other

words, it is what the graph is about.

Vocabulary Review

________________ ________________

__________________

_________

Range __________________

Observations _________________________________

Bins or Classes Horizontal Axis 20-29, 30-39,..

Frequency Vertical

Axis

Attribute

Spread Range of the Data

0-100

Observations Add the

Frequencies 1 + 2 + 1 + 2 + 6 + 9 + 13 + 5 =

38

A symmetric (bell shaped) distribution. It is also called a normal distribution.

If more than 30 people are sampled, the distribution is almost always normal. This means that

most of the data falls in the center and fewer data points fall at the extremes. The mean, median, and

mode are all the same.

Shape

Shape

A skewed right or positive distribution. Most of the

data falls toward the lower extreme. The plot looks like it has a tail to

the right.

A skewed left or negative distribution. Most of

the data falls toward the upper extreme. The plot looks like it has a

tail to the left.

Shape

Shape

A uniform distribution indicates that there

were similar or exact frequencies for each class in the sample.

Shape

The peaks on a histogram tell us the mode. What do you know about the

mode from this plot?

Steps to Creating a Histogram – Organizing the Data

•  Determine the highest and lowest values, and compute the range.

•  Divide the range into five or more sections with an equal number of values in each section. This creates your bin width.

•  Create a frequency table with the appropriate classes or bins on the left side and the number of values in each class on the right side with tally marks.

Steps to Creating a Histogram Creating the Display

•  Draw a horizontal axis and mark even spaces for your bins. Label the bins so the scale is clear and title your axis.

•  Draw a vertical axis and choose a scale that will accommodate the highest frequency. Label and title your axis.

•  Construct bars for each class of data that correspond to the frequency.

•  Give your histogram a title.

Organize Class Data

How many hours did you spend on electronic media last weekend? List the number of hours from 0-48 on your whiteboard and hold it up.

Follow Along as I Organize the Class Data.

Organize Class Data

First, I will find the highest and the lowest

values. ________    _______  

And find the range ______

Next, I will divide the range into at least five equal size bins.

This will give me class sizes of ________.

Finally, I will create a frequency table.

Hours on E-Media (Bins)

Frequency

Steps to Creating a Histogram Creating the Display

Weekend Electronic Media Use

Class Practice

Questions for Review: 1.  What is the attribute? 2.  How many observations are

recorded? 3. Can you find the mean, median, and

mode? 4. What is the spread of the data? 5.  Are there any outliers? 6. What does the shape of the histogram

reveal?

Class Practice

Create Histograms for the Data Sets

on Your Worksheet.

We will review as a class when we finish.

Organize Class Data

Interval (Candies Per Bag)

Frequency # of Values

21-­‐40   llll  41-­‐60   llll  61-­‐80   llll    ll  81-­‐100   ll  101-­‐120   lll  

Chocolate Candies per Trail Mix Bag

21-40 41-60 61-80 81-100 101-119

Organize Class Data

Interval Scores

Frequency # of Values

51-­‐60   l  61-­‐70   llll  71-­‐80   llll    llll  ll  81-­‐90   llll  91-­‐100   llll  

Test Scores, out of 100 Points

51-60 61-70 71-80 81-90 91-100

Organize Class Data

Interval (Temperatures)

Frequency # of Values

45-­‐49   llll  50-­‐54   llll  l  55-­‐59   llll    lll  60-­‐64   llll  65-­‐69   llll  70-­‐74   llll  

Daily High Temp(Fahrenheit)

45-49 50-54 55-59 60-64 65-69 70-74

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