=AVERAGE(Al:A10) gives the average of all the numbers in the cells from Al to A10 inclusive.

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1 What is a function? A function is simply a specialised calculation that Excel has memorised. There are many functions (around 200) built into Excel and they can do lots of different things. In this chapter just a few of them will be mentioned since many demand specialist knowledge for their use (e.g. accountancy, statistics, advanced maths and so on). We have already come across simple mathematical functions (e.g. add, subtract, multiply and divide). There are other functions you might find useful and some of the main ones are outlined here. Like a formula, a function needs to start with an equals sign and you also need to tell the spreadsheet which cells you want to use it with. A cell range from Al to A13 would be written as (Al:A13). Here are some of the most popular, simple functions. Notice they all start with an equals sign followed by the name of the function and then the range of cells the function is to be applied to. The range is put inside a pair of brackets. Average =AVERAGE(Al:A10) gives the average of all the numbers in the cells from Al to A10 inclusive. Maximum =MAX(E4:Ell) displays the largest number from all the cells from E4 to Ell inclusive. Minimum =MINIMUM(B2:B12) displays the smallest number from all the cells from B2 to B12 inclusive. Count Suppose we want to count the number of numeric entries in the range C3 to C30. We can use =COUNT(C3:C30) Any blank lines or text entries in the range are not counted. 1

2 Counta To count a number of items or names of people (not numeric entries, as above) we need to be able to count text entries. To do this we can use =COUNTA(C3:C30). You need to make sure that headings are not included in the range so that they are not counted as well. Again, blank lines are not counted. The IF function The IF function is very useful because you can use it to test a condition and then choose between two actions based on whether the condition is true or false. The IF function makes use of something called relational operators. You may have come across these in your mathematics lessons but it is worth going through what they mean. Relational operators ( =, <, >, <>, <=, >=) The most popular operator by far is the equals sign, but sometimes a comparison needs to be made between two items of data. For example, we may need to find a list of employees whose salaries are greater than a certain amount. Operators can also be used with characters or character strings, so one character can be compared with another and since each character has a binary code (ASCII) associated with it, the computer can work out that A comes before B and so on. You can also test to see if the contents of a certain cell have a certain word in them. For example, you could test to see IF B6="Yes". The IF function is structured like this: =IF(condition, value if true, value if false) The value can either be a number or a message. If the values are messages, then they need to be enclosed inside double quote marks (e.g. "High"). The commas within the brackets are essential to separate the different parts. Symbol Meaning Examples = equals = 10 > greater than 5*3 > 2*3 < less than -6 < -1 or 100 < 200 <> not equal to "Red" < > "White" or 20/4 < > 6*4 <= less than or ''Adam'' < = "Eve" equal to >= greater than 400 >= 200 or equal to 2

3 EXAMPLE: Choosing between two postage charges, In the following spreadsheet you will learn to: test a cell with an IF function and then to print a number dependant on whether the test is true or false. Suppose a mail order company has two charges for postage. If the order is 500 or over then the charge is 25, otherwise the charge is 15. In the worksheet shown, a column has been left blank so that the postage charge can be added. 1 Set up your worksheet so that it is exactly the same as shown below. A B 2 An IF function is needed to test the value in cell A1 to see if it is 500 or over. We express this condition in maths as greater than or equal to 500. This is written in mathematical language as > =500. Put the following IF function in cell B1: =IF(A 1> =500,25,15) Basically this formula means that if the charge is 500 or over then 25 will be placed in column B for the postage and if not then 15 is put in. 3

4 Note: Do not put the signs into the formula as it will no longer work properly if anything other than numerals are present. Your worksheet will now look like this. 3 This formula is now copied relatively down the rest of the column. 4 Your worksheet will now look like this: 4

5 Making sense of IF... THEN... ELSE statements Look at the following expression: =IF(A3 > 5,A6+ B2,A6-C2) This means that IF the number in cell A3 is greater than five THEN the contents of cell A6 will be added to those of cell B2, otherwise (ELSE) the contents of cell C2 are subtracted from those in cell A6. Teacher's markbook: using a range of functions In the following spreadsheet you will learn to: test a pupil's mark and then print 'Pass' or 'Fail' using an IF function print the average mark, the highest mark and the lowest mark for each group use the COUNTA function to count the number of pupils in each group. A teacher teaches two advanced level mathematics groups. Both groups have just taken a test and the teacher records the names and marks for each group in her mark book. The marks are all expressed as percentages. The headteacher has asked the teacher to set up a spreadsheet according to her instructions. You have to set up the spreadsheet following these instructions. 1) Load Excel and enter the data as follows: in cell A1 enter Group A in cell D1 enter Group B since these are both headings, increase the font size to 14 and embolden them in cell A2 enter Name in cell B2 enter Marks repeat this in cells D2 and E2 respectively now embolden all of this. 5

6 2 Now enter all the names of the pupils and their marks in exactly the same places as in the following worksheet. After entering the data you should verify it. This means making sure it is correct by comparing what you have typed with the data shown above. This method of verification is called proof reading. Remember that the data is the exam marks so it must be correct. 3) The pass mark for the examination was 55%. A message needs to be displayed next to the marks to indicate whether the pupil has passed or failed. In cell C3 enter the following formula: = IF (B3> =55,"Pass","Fail") Copy this formula relatively for the other pupils down column C. Now enter a similar formula (yes, you have to devise this for yourself!) and again copy it relatively, down column F. Check that your worksheet looks identical to the one below. 6

7 4) So that the performance of both groups can be compared, we will work out the following: the average mark, the highest mark and the lowest mark for each group. In cells A13 and D13 enter the text Average = In cell B13 enter the following formula to work out the average: =Average(B3:B11 ) Enter a similar formula in cell E13 to work out the average for group B. In cells A15 and D15 enter the text Highest mark= In cell B15 enter the formula to work out the highest mark: =MAX(B3:B11) In cell E15 enter a similar formula, but remember that there is one less pupil in group B. In cells A16 and D16 enter the text Lowest mark= In cell B16 enter the formula to work out the lowest mark: =MIN(B3:Bll) Enter a similar formula in cell E16. 7

8 5) As a check, to make sure that all the required pupils have been included, the headteacher has specified that the total number of pupils in each group should be shown. Enter the text Number of pupils= into cells A20 and D20. Now enter the formula into cell B20 to work out the number of pupils. Since we are going to count the names (i.e. text) we use the COUNTA function in the following way: =COUNTA(A3:A11) Now use a similar formula to count the number of pupils in group B and place the answer in cell E20. If you have done everything correctly, your worksheet will look like this 8

9 The Lookup function Lookup functions are very useful; they work as follows. When you enter data the spreadsheet looks through a table until it finds a match along with other important data. For example, if each product in a shop is given a unique number, we can store this number along with a description of the product, price, etc. in a table in another part of the spreadsheet. If we then type in a product number in another part of the spreadsheet, the spreadsheet searches through the table until it locates the product number and related details. This sounds quite complicated, so let's look at an example. Creating a lookup table: supermarket products and prices In the following spreadsheet you will learn to: create a lookup table and use the VLOOKUP function. 1 Key in the data exactly as it is shown in the screen above. Do not type in the values for the cells B5 and B6 as these contain formulae that will be entered later. 2 Check that all the data is in the same position as the screen shown and that all the values are the same. 9

10 3 Cells B5 and B6 contain formulae. In cell B5 type the following formula: =VLOOKUP(B4,A11 :C14,2,FALSE) and in cell B6 type the following formula: =VLOOKUP(B4,A 11 :C14,3,FALSE) In order to use the LOOKUP function we have to understand how it works. Looking at the formula in cell B5, =VLOOKUP(B4,A11 :C14,2,FALSE). 10