Andrew Mead (School of Life Sciences) LDC Statistics Seminars, 2013/4 Measurements, Meaningfulness and Scale Types.

Andrew Mead (School of Life Sciences)

LDCStatistics Seminars, 2013/4

Measurements, Meaningfulness and Scale Types

2

The Nature of Measurement All studies (experiments or surveys) involve some

sort of measurement Important part of the planning for any study What are you going to measure?

How accurately can you measure it? What is the precision of your measurements? Can you measure what you are really interested in? How do the data relate to the real response of interest?

Different types of measurement require different statistical approaches Important to consider method of analysis when

planning the form of measurement

3

How far is an Irish mile?

Knappogue Castle,Co. Clare

5

6

0

2

4

6

8

10

12

14

0 5 10 15 20

English mile

Iris

h m

ile

English Irish Ratio

Quin 2¼ 1¾ 1.286

Spancilhill 6¼ 5 1.250

Ennis 8½ 6½ 1.308

Kilkishen 4 3½ 1.143

Sixmilebridge 5¾ 4½ 1.278

Limerick 15½ 12¼ 1.265

Mean ratio =1.255 =>

1 Irish mile = 2208 yds

In fact, 1 Irish mile = 14/11 (= 1.273) English miles!EM = 1760 yds; IM = 2240 yds

7

The Need for Statistics Statistical methods have been developed to

help in the quantitative study of variation and the summary, analysis and interpretation of data from experimental and observational studies.

Important to understand the nature of the measurements being made to be able to identify the most appropriate method of analysis

Important to also consider the nature of measurements for the presentation of data and the results of analyses