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is the science of the collection, organization, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments.
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STATISTICS Class intervals a set of numerical data that is grouped into several classes and the range of each class is known as class interval
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There should be between 5 and 20 classes. The class width should be an odd number. This will guarantee that the class midpoints are integers instead of decimals. The classes must be mutually exclusive. This means that no data value can fall into two different classes
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The classes must be all inclusive. This means that all data values must be included. The classes must be continuous. There are no gaps in a frequency distribution. Classes that have no values in them must be included (unless its the first or last class which are dropped). The classes must be equal in width.
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Class intervals Find the largest and smallest values Compute the Range = Maximum - Minimum Select the number of classes desired. This is usually between 5 and 20. Find the class width by dividing the range by the number of classes and rounding up. Pick a suitable starting point less than or equal to the minimum value.
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Class Boundary-lower boundary is the midpoint between the lower limit of the class interval and the upper limit of the previous class interval- Upper boundary is the midpoint between the upper limit of the class interval and the lower limit of the succeeding class interval
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HISTOGRAM bar chart with i. horizontal axis represented by the upper boundary and the vertical axis represented by the frequencyOr ii. frequency versus midpoint
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Frequency polygon Frequency polygon of marks 10 9 8 7Frequency 6 5 4 3 2 1 0 34.5 44.5 54.5 64.5 .74.5 84.5 94.5 104.5 Midpoint (marks)
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Cumulative Frequency Table Must add a class interval with 0 frequency
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Ogive : Cumulative frequency curve Cumulative frequency versus upper boundaries
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Ogive of marks 45 40 35Cumulative frequency 30 25 20 15 10 5 0 29.5 39.5 49.5 59.5 69.5 79.5 89.5 99.5 Upper boundary ( marks )
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Measures of Dispersion - the amount or distances the values are spread out in a set of data i. Range :midpoint of the highest class – midpoint of the lowest class ii. Median : the value at half of the distribution iii. First quartile(Q1): the value at the first quarter iv. Third quartile (Q3): the value at the third quarter v. Interquartile range : Q3 – Q1
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Ogive of marks 45 40 35Cumulative frequency 30 25 20 15 10 5 0 29.5 39.5 49.5 59.5 69.5 79.5 89.5 99.5 Upper boundary ( marks )
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