3.1.1 ICT Check Digit

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  • Created by: Bellaxox
  • Created on: 06-11-17 08:42
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  • ICT AS 3.1.1
    • Check Digit
      • Modulus 11 check digit
        • When using this the last digit is always 2
        • The first digit is the length of the digits add 1 e.g. length is 5 so its 5 + 1 = 6 therefore 6 is the first digit
        • The middle digit go down in scale e.g. 5,4,3,2 these are the numbers between the first and last digit
        • You then multiple the digit by the weight
        • You then add all the multiples together
        • You then divide this by 11
        • Divide the remainder e.g. 6.7 by 11
        • Example
          • 9317
            • Length of digit is 4
            • Last digit is 2
            • First digit is 4 + 1 = 5
            • Middle digits (weight) are 5,4,3,2
            • Digit = 9137
              • Weight = 5432
                • Multiple = 9*5 = 45, 1*4 = 4, 3*3 = 9, 7*2 = 14
                  • 45 + 4 + 9 + 14 = 72
                    • 72 / 11 = 6.6
                      • 11 - 6 = 5
                        • Check digit = 93175
      • Check digit
        • Is an extra digit added to the end of a data number
        • An extra digit is the result of a calculation
        • The calculation is peformed on the original data
        • The check digit that is entered is compared with the check digit the computer calculates
        • How to:
          • 1. Add the odd number positioned digits together e.g. 1,3,5
        • Example
          • 98377102 9+3+7+0 = 19
            • 19 * 3 = 57
              • 8+7+1+2 = 18
                • 57 + 18 = 75
                  • 75 / 10 = 7.5
                    • 10 - 5 = 5
                      • Check digit 983771025
          • 70970156 7+9+0+5 = 21
            • 21 * 3 = 63
              • 0+7+1+6 = 14
                • 63 + 14 = 77
                  • 77 / 10 = 7.7
                    • 10 - 7 = 3
                      • 709701563
      • ISBN Check Digit
        • ISBN are 10 characters long
        • It is 9 digits + the check data
        • The weight is 10  as it is 9 + 1
        • it descends down in order
        • Example
          • ISBN =        0-201-67281
            • First digit = 10 (9+1)
            • Last digit = 2
            • 0*10 = 0, 2+9 = 18, 0*8= 0, 1*7 = 7, 6*6 = 36, 7*5 = 40, 2*4 = 8, 8*3 = 24, 1*2 = 2
              • 0 + 18 + 0 + 7 + 36 + 40 + 8 + 24 + 2 = 135
                • 135 / 11 = 12.3
                  • 11 - 3 = 8
                    • ISBN = 0-201-672818
        • 1. Find the weight (length of number add 1)
          • 2. Multiple the digit by weight
            • 3. Add the numbers from 2 together
              • 4. Divide the result of 3 by 11
                • 5. Identify the remainder of the result from 4
                  • 6. Subtract the remainder from 11 to get the check digit
      • The highest weight is calculated by adding 1 to the length of the number
    • Types of data
      • Direct
        • Gathered from an original source
      • Indirect
        • Gathered from another source or as a by product of another operation
      • Sources of data
        • Direct data source is it used for the same purpose for what it has been collected.
          • Advantage
            • The data that is collected is the data needed
            • The original source data can be trusted
          • Dis-advantages
            • Can be costly to collect original data (e.g. phone calls)
            • It can take time to collect the data and may not be ready in time
            • If statistical data is required then it may not be possible to get a large enough sample of data
        • Indirect data is the data is used not for the same purpose it was collected for, the data is used for a different reason it was collected for.
          • Advantages
            • There is no need to wait for the data to be collected as its already available
            • Various difference sources of data can be used and compared to verify the accuracy of the data
            • More likely to be a large sample of data is statistical analysis is required
          • Dis-advantages
            • The data may not meet all of the needs of the new purpose of use
            • The data maybe out of date if it was collected a long time ago
            • The source may not be trustworthy as collecting it directly because it was collected a different time for a different purpose
            • Only summary information maybe available rather then the detail required
            • The original data maybe biased. For example names and addresses from a football club maybe male dominated
            • The data maybe presented in a format that makes it difficult to extract the information required
      • Static
        • Data can not be changed, i.e. a book, dvd
        • Advantages
          • No risk of virus
          • No need for internet connection
          • Can be reliable as they have been produced for a reason
          • Information likely to be more relevant
        • Dis-advantages
          • Limited info
          • Books and CD's take long time to produce
          • Books and Cds can be damanged
          • Only one person can use them at a time
      • Dynamic
        • This is data that can be changed i.e. electronically stored data like a news article online
        • Advantages
          • More likely to be up ti date
          • Hyperlinks can be used to visit relative sites or info
          • Many users can visit the website at a time
          • Wide range of results therefore a good chance of finding what you need
        • Disadvantage
          • Not always accurate
          • Location of pages can change
          • Malware damage
          • Internet access needed
          • Wide range of unneeded results
      • Quality of data
        • Gigo (Garbage in, garbage out)
          • If data input is poor the resulting information output will be poor
          • Example: If register is filled in wrong it will have the wrong output
          • Six Facts to make Gigo
            • Age, how old/ up to date it is
            • Accuracy, need to be accurate to be reliable
            • Completeness, only having part of information is worthless
            • Relevance, it must be relevant
            • Presentation, must be presentable
            • Level of detail, given either too much or too little
    • Encoding data
      • Replacing data with shorter data
        • E.g. January - Jan, February - Feb
        • It is not encryption where it is scrambled until you unlock it
      • Reasons for encoding
        • Less chance of spelling or incorrect data input
        • Reduce the amount of storage needed
        • Improve presentation
        • Secure
        • Speeds up processing time
      • Numerical data
        • Assigning numbers to data
          • E.g. 1 being science, 3 being phone, 11 being Jade
        • Dis-advantages
          • System can make no sence
          • Not always clear on the number e.g. 2077 could be 2,0,77
      • Abbreviation
        • Uses a shortened version of the data
        • Uses letters from original text
        • E.g. SCI - science, ENG - English,
        • Dis-advantage
          • Shorting it to three letters work for certain things but not all e.g. Art
      • Value judgement
        • Usually used in questionnaires
        • E.g. Rate the quality from 1 to 10
      • Advantages to encoding
        • Less data to store
        • Speed of processing, smaller data items being processed
        • Speed of input
        • Validation, length, range and format checks
        • Presentation
        • Confidentiality, data maybe meaning less without knowledge of coding method
      • Dis-advantages
        • Interpretation, B75 is Birmingham or Brighton
        • Accuracy, data entry requires every character to be legible
        • Completeness, some data can be lost
        • Limited codes, codes can run out
        • Value judgement, someones 9 might be different to someones 6, people interpreter things differently.
  • Indirect
    • Gathered from another source or as a by product of another operation

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