Descriptive Stats Booklet 4

Name 3 measures of Central tendency

Mean, mode, median

How do you calculate the mean?

All scores are added together and divided by the number of scores

How do you calculate the median?

All scores are put in order and the middle score is identified

How do you calculate the mode?

Find the most commonly occurring score.

Give a strength and limitation of using the mean

Strength: All scores are taken into account therefore more representative of all the data

Limitation: It can be skewed by extreme scores (distorted- making it higher or lower than it should be)

Give a strength and limitation of using the median

Strength: Not skewed by extreme scores.

Limitation: It does not take into account all scores.

Give a strength and limitation of using the mode

Strength: Only measure that can be used on all types of data

Limitation: There may be several modes. Ignores all other scores.

When do you use the mean?

When there is no extreme scores

When do you use the median?

When there is 1 or more extreme scores

When do you use the mode?

Can be used on any data but usually when the data is categorical

Define normal distribution

The mean, mode and median are roughly the same

What is meant by positive skew?

The mode is lower than the mean.

What is meant by negative skew?

The mode is higher than the mean.

What are the 2 measures of dispersion?

Range and Standard deviation

Why is it better to use standard deviation rather than the range for a set of data?

The standard deviation is a more accurate measure of dispersion, as it takes into account the distance every score is from the mean.

If the standard deviation is low, what does this suggest?

There is little variation in scores (they are clustered around the mean)

If the standard deviation is high, what does this suggest?

There is greater variation/spread in the scores.