central tendency and measures of spread

Question 1

3 measures of central tendency

Answer 1

• mean, median, mode

Question 2

what is the mean

Answer 2

The mean of a dataset is the SUM of the dataset divided by the number of individuals (n)

Question 2

what is the median

Answer 2

The median value is the middle value of a dataset when the dataset is listed in numerical order (ranked)

Question 3

what is the mode

Answer 3

The mode of a dataset is the value that occurs most often

Question 4

why are central tendency data often so different?

Answer 4

Mean vs Median

Mean is very sensitive to extreme values

Median is much less sensitive (robust)

Question 5

why is the mode rarely used for quantitative data?

Answer 5

In such a small dataset comprising INTERVAL data the chances of a value occurring more than once are low
The mode is rarely used for quantitative data except in specific cases such as technical analysis e.g. interpretation of particle-size analyses

Question 6

When to use which Central Tendency?

Answer 6

Nominal data (categories) → use the mode

Quantitative data → use the mean or the median

Use the median when extreme values are present and you donʼt want a distorted average

Use the mean when extreme scores are absent

Question 7

Why use Measures of Spread?

Answer 7

Measures of central tendency give us ʻtypicalʼ values of dataset

…but this is not enough
Very different datasets may have very similar MEAN/MEDIAN
…so we need to also describe the spread of the data

Question 8

Ways to quantify Measures of Spread?

Answer 8

Four main techniques are used in Geography
- Range
- Inter-quartile range
- Standard deviation
- Variance

Question 9

Problems with using the range

Answer 9

The range is very sensitive to sample size and extreme values.

Question 10

Variance

Answer 10

• The variance is very similar to the standard deviation and uses almost the same equation
  -The only difference is that you donʼt calculate the square root