Yet there is considerable opposition to the use of genetically modified plants for food production and other uses. Genetic engineering offers a time-saving method for producing larger, higher-quality crops with less effort and expense. You are a tomato farmer whose crops are threatened by a persistent species of beetle. 2  Each year, you spend large sums of money for pesticides to protect your crops.
To calculate the variance follow these steps: 1  Work out the Mean (the simple average of the numbers). 2  Then for each number: subtract the Mean and square the result (the squared difference). 3  Then work out the average of those squared differences.
Calculate the mean, x. 1  Write a table that subtracts the mean from each observed value. 2  Square each of the differences. 3  Add this column. 4  Divide by n -1 where n is the number of items in the sample This is the variance. 5  To get the standard deviation we take the square root of the variance.