Manipulating data Data management validation and verification Manipulating

Manipulating data Data management: validation and verification

Manipulating data Valid data • Data that is valid is allowable • Valid data has to obey certain rules • Data can be incorrect yet still valid

Manipulating data Data can be valid and incorrect Example: • A person has a date of birth 19/12/87 • A user enters it incorrectly as 19/12/78 • Both are valid as dates • Yet one is incorrect

Manipulating data Two techniques for reducing errors • Verification • Validation

Manipulating data Verification • Checks that errors are not introduced during typing by the user • Checks data entered is the same as on a source document (e. g. , order form, application form, etc. )

Manipulating data Two methods of verification • Visual checking/proof reading – checking what has been typed in against a source document • Double entry of data – two people enter the same data – only if both sets of data are the same will it be accepted

Manipulating data Validation checks include • Data type checks – is data entered the right type for the field (e. g. , letters are not entered into a numeric field)? • Presence checks – has a field been left empty? • Format checks – is data is of the right length and the right combination of characters for a field (e. g. , code FF 019 J has length 6 characters with first two letters, the next three numbers and the last a letter)? • Range Checks • Look-up Lists • Format Checks • Check digits

Manipulating data Parity checks Ensure that data sent over a network has not become corrupted

Manipulating data Hash and Batch Totals created from the data that is meaningless apart from checking that the data is verified. See - Animation

Manipulating data Spreadsheet software

Manipulating data Spreadsheets

Manipulating data Components of spreadsheets • Labels - are used for titles, headings, names, and for identifying columns of data • Data - are the values (text or numbers) that you enter into the spreadsheet • Formulas - are used to perform calculations on the cell contents

Manipulating data Functions • A function is a specialized calculation that the spreadsheet software has memorized • Average • Max, Min • Mode, Median • Sum • Count, Counta, Countif • Vlookup • IF

Manipulating data The two types of cell referencing • Relative cell referencing • Absolute cell referencing

Manipulating data Relative cell referencing • This reference tells the spreadsheet that the cell to which it refers is 3 cells up and one cell to the left of cell B 4 • If cell B 4 is copied to another position, say E 5, then the reference will still be to the same number of cells up and to the left so it will now be to cell D 2.

Manipulating data Absolute cell referencing • With absolute cell referencing, if cell B 4 contains a reference to cell A 1, then if the contents of B 4 are copied to a new position, the reference will not be adjusted and it will still refer to cell A 1

Manipulating data The benefits of using spreadsheets • You can perform ‘what if’ investigations – you can make changes to the spreadsheet values to see what happens • Automatic recalculation – when an item of data changes, all those cells that are connected to the changed cell by a formula will also change • Accurate calculation – provided the formulas are all correct, the calculations on the numbers will always be correct • It is easy to produce graphs and charts – once the data has been entered, it is very easy for the spreadsheet to produce graphs and charts based on it

Manipulating data Graphs and Modelling • Pie, Bar, Scattergraphs, line • Modelling – – – Inputs Variables Constants Contraints Rules Have a go at the activity 1 - 4 on page 86

Manipulating data Data capture

Manipulating data Data capture 1 • Is the method by which data from the outside world enters the computer for processing • For example, keyboard entry is a method of data capture • Other methods include optical mark recognition, the use of sensors, etc.

Manipulating data Data capture 2 The ideal method of data capture would be: • Comparatively accurate • Cheap • Automatic • Fast

Manipulating data Chip and pin • Used to capture credit/ debit card details • Details are encrypted on a chip • User has to enter a PIN that only they know • The PIN is checked and proves the user is authentic

Manipulating data Optical mark recognition (OMR) • Automatically reads marks made on a form • Forms are read/scanned at high speed • Readers are relatively cheap • Reject rate owing to people not filling in the form correctly can be high • If forms are folded they cannot be read

Manipulating data Bar code reading • A code is stored as a series of light and dark bars • Uses a scanner to read the bars • Used on items in stores, parcels, luggage handling at airports, etc. • Fast to read • Accurate • Can be read at a distance

Manipulating data Voice recognition • Uses microphone as the input device • Uses special voice recognition software to turn the sounds into letters that can be understood • Can input text into wordprocessing, email software, etc. , using speech • Can also issue commands using speech

Manipulating data Biometrics • Uses unique features of the human body to recognize a person • Examples include retinal scanning, fingerprint recognition, etc. • Ideal for access control to buildings, rooms and computers • Has the advantage that, unlike passwords, there is nothing to remember

Manipulating data RFID tags • RFID means radio frequency identification • Data is stored on a small computer chip • Tags can be read at a distance • Tags can be read through clothing or a bag • They can store a lot of data • They are quite expensive to manufacture

Manipulating data Databases

Manipulating data A Database • Fields – Key fields / Primary key • Record • File – Table • Flat file and relational databases – Data redundancy – Keeping important data when deleting records – More efficient when doing searches.

Manipulating data Data Handling Applications • • Financial Forecasting Weather Forecasting Flight Simulators Expert Systems for decision making

Manipulating data Data handling software

Manipulating data Data handling software Covers any software used to store and manipulate data and output information: • • Database software Spreadsheet software

Manipulating data Updating, deleting and searching records • Update – change the data to bring up-todate • Delete – remove data no longer needed • Search – look for specific records that match certain criteria (e. g. , list the names of all students in Year 11)

Manipulating data Search criteria using operators Operators are used to construct search criteria and include: = equals > greater than < less than <> not equal to >= greater than or equal to <= less than or equal to

Manipulating data Examples of operators being used = Patel (In a surname field finds data for people with surname Patel) = 20 (In a quantity field finds data for all occurrences where the quantity is 20) >01/02/10 (In a date field finds the data for all the dates after (but not including) 01/02/10) <>0 (In a quantity field finds the data where the quantity does not equal zero)

Manipulating data Joining operators Operators can be joined by AND or OR Size = XL AND Type = Shirt The above will find all the extra large shirt details Pet = Dog OR Pet = Cat The above will find details for Dog or Cat

Manipulating data What do these searches do? Pupil ID Surname Age Free meals Form 11901 Duggan 15 N 11 G 11809 Hughes 15 Y 11 T 11900 Lee 15 N 11 T 11907 Liu 15 Y 11 G 11877 Khan 16 N 11 M 1 2 3 4 5 Pupil ID = 11809 Age > 15 Free meals = Y AND Age > 16 Form = 11 T OR Free meals = Y Surname = Lee

Manipulating data Answers to check 1 2 3 4 5 Displays one record for pupil with pupil ID 11809 (i. e. , pupil with surname Hughes) Displays all the details of pupils whose age is over 15 (i. e. , the details of all 16 -year-old pupils in this set of data) Displays data of all pupils who have free meals and are over 15 (i. e. , all 16 year olds in this case) Displays data for pupils who have free meals or who are in Form 11 T Displays the details for pupils with surname Lee