Frequency Diagrams By Mr. Swatanter Singh PGT (ECO.) KV HISAR CANTT.

Previous knowledge testing What do you mean by presentation of data ? What is frequency ? What is bar diagram ? What is cumulative frequency ? What is continuous variable ?

Types of frequency diagrams Histogram Frequency polygon Frequency curve Ogive

Histogram Histogram is a graphical presentation of frequency distribution. It is in the form of adjacent rectangles. It is a two dimensional diagram. It means height and width of rectangular bars both are important for the comparison of data.

Histogram Marks No. of students 10-20 3 20-30 13 30-40 30 40-50 22 50-60 12 60-70 2

Frequency Polygon Two methods Ist method : Frequency Polygon is drawn by joining the mid points of the top sides of the consecutive rectangles. IInd method :The frequency polygon may be drawn by connecting points plotted against the frequencies at the midpoints of the classes.

Frequency Polygon Ist method Marks No. of students 10-20 3 20-30 13 30-40 30 40-50 22 50-60 12 60-70 2

Frequency Polygon IInd method Marks No. of students 10-20 3 20-30 13 30-40 30 40-50 22 50-60 12 60-70 2

Frequency Curve Frequency curve is a smooth free hand curve passing through the points of frequency polygon as closely as possible.

Frequency Curve

Ogive Ogive is a cumulative frequency curve. Two Types : Less than Ogive : is obtained by joining the points for cumulative frequencies plotted against the upper class limit of class intervals. More than Ogive : is obtained by joining the points for cumulative frequencies plotted against the lower class limit of class intervals.

Less than Ogive Marks No. of students Less than Ogive 10-20 3 20-30 13 16 30-40 30 46 40-50 22 68 50-60 12 80 60-70 2 82

More than Ogive Marks No. of students Less than Ogive 10-20 3 20-30 13 16 30-40 30 46 40-50 22 68 50-60 12 80 60-70 2 82

Determination of median Median is the value corresponding to the intersection point of less than and more than ogives.

Uses 0f Frequency Diagrams to display large amounts of data in a relatively simple chart form. to tell frequency of occurrence. to easily see the distribution of the data. to see if there is variation in the data. to make future predictions based on the data. Here, I name some of the uses for a Histogram. I tell what makes this tool useful in making quality improvements. Since the histogram is such a useful tool, it can have many uses. Histograms can be used to display large amounts of data in a simple chart view. They can be used to find any patterns that the data might reveal. They can be used to tell relative frequency of occurrence for certain data values. They can also be used to see the distribution, or any variations in the data values. One other use would be to make predictions regarding the future based on the way the data values pan out.

Exercise Income No of employees Define histogram. Define frequency polygon. Plot histogram and frequency polygon for the given set of data: Define ogive. How Median is graphically determined ? Income 1000-2000 2000-3000 3000-4000 4000-5000 5000-6000 No of employees 20 25 10 50 15

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