In such a case, the median is a better measure of central tendency. This figure also shows the position of the mode relative to the median and mean. It should be clear why the mode is the lowest of the three in a positively skewed distribution - the peak is below the point that divides the distribution into two equal halves. Similarly, the mode is the highest measure of central tendency in a negatively skewed distribution. Psychological variables are typically unobservable and hence we can never be entirely confident that our measuring instruments have interval or ratio properties in relation to the properties of the underlying variables they claim to represent.
Some psychologists argue that at best our data are ordinal in nature.
If this is true, then as explained above, the mean is not an appropriate measure of central tendency. On the other hand, some psychological statisticians claim that it doesn t matter wha manipulations we perform upon our data - the numbers don t know where they co from . If twogroups have different means on some measure, then we have still demonstrated something interesting, and our task is then to make some psychological sense of it. There is no right answer to this question, and you will probably find tha members of staff in this department hold varying views about it. This is a personal page published by the author.