Part II Collecting and analysing data 8.2.3. Multiplication and division Multiplication and division is useful if you want to convert a numerical value into a percentage, or vice versa. For example, say you want to find out how much (in USD) is spent on healthcare, in total, in your country. You know GDP is USD 100,357,000,000 and that government spending on health is 3.48% of GDP. You can answer your question by using the following formula: GDP * (health spending/100) Or in a spreadsheet =100357000000*(3.48/100) You do not need to manually type in the numbers, clicking in the cell will do this for you. As shown in the spreadsheet below, the formula looks something like: =C2*(D2/100), where cell C2 is your country’s GDP and cell D2 is health expenditure as a percentage of GDP in your country. Copying formulae is useful when you want to apply the same calculation across rows or across columns. To do this, simply copy the formula you have just written (using ctrl + c ) and paste it into the cell below (using ctrl + v ). Alternatively, click on the lower right corner of the cell (the blue square) and drag the formula down to the end of the column. Empty cells can be problematic when you start to analyse your data because they can end up producing zero values. For example, if you copied the formula in the previous step to the end of the column you would see that the health expenditure in USD value for Bermuda would be “0” because the value for health expenditure as a percentage of GDP is missing. This is obviously a mistake. Properly handling missing values is an important step in data cleaning and analysis. Large datasets are rarely complete and so you should have a strategy to deal with missing parts. One way to find errors is to filter the data, select all “0” values and delete them. 8.3. USEFUL MATHEMATICAL CONCEPTS FOR ANALYSING DATA Ordering data to help answer your research questions can be daunting if you are trying to compare multiple variables. For instance, if you are looking at data that relates to the right to food, you might want to look at: (a) per capita availability; (b) of major food items; (c) across municipalities. You might be interested in finding out what is the average availability for these items, the minimum and maximum available, and the difference, or the variation, between the minimum and maximum. Finding out the answers to these questions is commonly referred to as descriptive statistics. Chapter 8: Analysing data: A short introduction to working with spreadsheets | 89