Loading Psychology Averages and Range…
Quick guide: plain English, key facts and method
In plain English: An average is one number that sums up a whole set of scores. The range tells you how spread out the scores are.
Key facts
- Mean = add up all the scores, then divide by how many there are.
- Median = the middle score once the scores are in order. Its position is (n + 1) ÷ 2.
- Mode = the most common score. It is the only average you can use with nominal data (categories).
- Range = highest − lowest.
- One extreme score distorts the mean but not the median.
How to do it
- Write the scores out in order first. It makes every other step easier.
- Mean: find the total, then divide by n.
- Median: work out (n + 1) ÷ 2 and count in to that position.
- Frequency table: multiply each score by its frequency (fx), add these up, then divide by the total frequency (Σf).
Memory aid: Mean: interval data with no extreme scores. Median: ordinal data, or interval data with an extreme score. Mode: nominal data (categories).