On day 19 we extend our understanding of averages by looking at Grouped frequency tables. Here you will find that your data has been grouped into categories. It is important to note a change in the vocabulary for the questions. Because the data is grouped, you will be unable to use specific values as you don't know what they are hence you will be asked to find an estimate for the mean or an estimate for the median.
You will often have to create two extra columns, one for the midpoints of each group and one for your fx column.