What is Histogram | Histogram in excel | How to draw a histogram in excel?

A Histogram is a pictorial representation that shows the frequency distribution of numerical data.

Histogram displays the data in bar where each bar indicates the frequency (called a “count”) of data points or measurements that fall within a specific interval or range (called a “bin”).

It is created by grouping the measurements into “cells” or “class ” or “bins”.

Histogram is similar to the bar chart, but it groups data points into classes and plot frequencies. Bar chart is used for categorical data, but a histogram is used for quantitative (numerical) data only.

Histogram graph is considered one of the basic 7 QC Tools or Seven Basic Quality Improvement Tools and is extensively used in SPC, Lean Manufacturing, and problem-solving techniques such as 8D, PDCA, and  Six Sigma.

WHEN TO USE A HISTOGRAM

• To summarize large data sets graphically.
• To compare measurements to specifications.
• Assist in decision making.

PURPOSE OR BENEFITS OF HISTOGRAM

• A bar graph that shows the frequency distribution of values/data.
• To assess process capability & to understand variation.
• Useful to understand the spread or variations, and distribution in a process.
• To visualize shape of the data-normal, bimodal, skewed etc.
• To know whether a process is stable and predictable.
• To know whether the process produces within specification.
• Process monitoring and centering.
• Helps in decision-making based on the behavior of data.
• To capture process shifts and abnormalities.

HISTOGRAM IN EXCEL | HISTOGRAM WITH EXAMPLE

Steps for constructing a Frequency distribution graph or Histogram in excel are as follows:

1-Count the number of data points ‘n’.

2- Compute the range of data. The range ‘R’ is the difference between the largest and the smallest value in the sample.

3- Determine the number of classes or intervals i.e. class size

4- Compute class width.

5- Prepare the Tally sheet or Check sheet by summarizing data on it.

6- Count the number of parts in each interval i.e. Number of frequencies within a particular class.

7- Now plot the graph. Place frequencies on the vertical axis, and class intervals on the horizontal axis.

8- Interpret the histogram by seeing the shape distribution.

Histogram I Key Components

Key Components	Description
X-axis	Represents the class intervals (bins) of data (e.g., size, weight)
Y-axis	Represents the frequency (how many times values fall in each bin)
Bars	bar height shows how many data points are in that class intervals or range
Bin Width	The range covered by each bar

INTERPRETATION OF HISTOGRAM

Histogram Shapes	Interpretation
Normal (bell shape)	Indicates that the process is stable and consistent
Skewed Left	More values at high end, indicates that the defect at low end
Skewed Right	More values at low end, indicates overshooting specification
Bimodal	Two peaks – may suggest two machines or shifts with different performance
Uniform	Equal frequency – indicate possibly random process

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