1. Descriptive Statistics
Introduction to Study Skills & Research Methods (HL10040)
Dr James Betts

2. Lecture Outline: Statistics Variables Levels of Measurement
Measures of Central Tendency
Distribution
Variability.

3. Statistics
Descriptive
Inferential
Correlational

4. Nominal Scale
Ordinal Scale

5. Interval Scale
Ratio Scale

6. Quick Test Nominal, Ordinal, Interval or Ratio?
Blood lactate concentration (mmol.l-1)
Profile of Mood States (scale 1-7)
Heart Rate (beats.min-1)
Blood Group
Bench Press 1RM (kg)
Year of Birth (AD)
Atmospheric Pressure (mmHg)

7. Système Internationale (SI) Units
Seven ‘constant’* base units using the metric system
Variable
Unit
Symbol
Accepted Derivations
Distance
metre m
ha for area; º for angle; #l or L for volume
Mass*
kilogram kg t
Time
second s
min, h, d (not year)
Temperature
kelvin K
Mole
mole
mol
#l or L for volume
Current
ampere A
Luminance
candela cd
Units always lower-case#, neither italicised nor pleuralised (i.e. kg not KGS) and with space between value and unit (inc. % but exc. º).

8. Discrete and Continuous Variables
Discrete Variables:
Continuous Variables:

9. Indicators of Central Tendency
Mode
Most Frequently Occurring Score
Median
Middle Score
Mean
Arithmetic Average.

10. Normal Distribution

11. Normal Distribution

12. Normal Distribution

13. Non-Normal Distribution

14. Hypothetical Investigation
“The effect of 1 week placebo supplementation on press-up performance”
8 randomly sampled participants
Performed as many press-ups as possible
Supplemented with placebo tablets for 1 week

15. Mean  SD

19. Standard Error of the Mean (SEM)
68.26%
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Number of Press-ups

20. Standard Error of the Mean (SEM)SD n
SEM =

21. Mean  SEM

23. Median & Range or IQR
The mean  SD or SEM cannot be used for non-normally distributed data
Instead the median is often plotted along with either the range or the IQR
Raw Data: 8, 10, 15, 20, 55, 75, 120, 179

25. Put the data from each trial into SPSS…
Week 2
Week 1

26. Select ‘Analyze’, ‘GLM’, ‘Repeated Measures’…

27. Move variables from here…
…to here, click ok

28. ANOVA Output
MSE n
nCI =
[criterion t (df)]

29. t – Distribution Table Degrees of Freedom Critical t-ratio 1 2 3 4 5 6
(Google Search)
Degrees of Freedom
Critical t-ratio 1 2 3 4 5 6 7 8
12.71
4.30
3.18
2.78
2.57
2.45
2.37
2.31

30. Mean  nCI

31. Selected Reading
Hopkins W. G. (2000) A New View of Statistics [Online] Auckland: Internet Society for Sport Science. Available at: [accessed October 3rd 2005]
Masson, M. E. J. and G. R. Loftus. Using confidence intervals for graphically based data interpretation. Canadian Journal of Experimental Psychology. 57: , 2003.