11.1.8 More About Data

So far in this unit, you have discovered how to describe a set of data by looking at a typical value, an average value. You have learned how to find three kinds of average: mean, median, and mode. You have also seen how to measure the spread of data using the range.

Averages are used frequently in reports and in the media to summarize data. When you come across an average in this way, it’s worth asking yourself some questions before drawing any conclusions.

  • Do you know what kind of average was used?
  • How many values were used to calculate the average?
  • How was the data collected?

Then, you’ll be prepared to consider the data, and the type of average used, in a critical manner.

Notepad iconActivity: How Many Data?

Write down some ideas about why you think that the number of values collected is something to consider?

Solutions icon

Answer

The more data that has been used to calculate the average the more likely it is to be a reliable result.

When averages are calculated this may be based upon a sample of the total data available rather than all the data, particularly when dealing with large populations.

For example if you wanted to know the average height of men in a country, it would be impractical to measure and record this value for all men—so a sample of the population would be taken. The more measurements you had from across the whole country, the better idea you would get of an average value for the whole population. As well as this, the more data that you have, the less influence extremes can have on the average if the mean is used.

Now we have looked at a few ways to analyze data, let’s move on to how to present this using tables, graphs, or charts making data easier to understand .

11.1.7 Measuring the Spread of a Data Set