Week 3 Descriptive stats

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Lecturer: Chee- Wee Tan Module: P1112 Introduction to Research University: Queen Margaret University, Edinburgh

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Descriptive Statistics: 

Descriptive Statistics Chee-Wee Tan Module P1112

What are descriptive statistics?: 

What are descriptive statistics? Summarising data Spotting patterns 6186458166186458164563816458163456184658164516465

Case Study: 

Case Study Drink kryptonite -- More push-ups? 1 6 1 2 6 1 2 2 10 3 4 9 4 5 7 5 6 6 6 2 6 6 9 7 7 8 8 9 9 3 3 10 2 1 10 2 10 10 10 6 6 6 9

Histogram: 

Histogram

Distributions: 

Distributions Normal Distribution

Skewed Distributions: 

Skewed Distributions Positively skewed Negatively skewed

Kurtosis: 

Kurtosis Leptokurtic distribution platykurtic distribution

Measures of Central Tendencies: 

Measures of Central Tendencies Mode Used with nominal data Bimodality may be messy to deal with.

Measures of Central Tendency: 

Measures of Central Tendency Median 1 1 1 1 2 2 2 2 2 2 3 3 3 4 4 5 5 6 6 6 6 6 6 6 6 6 6 7 7 7 8 8 9 9 9 9 9 10 10 10 10 10 10

Measures of Central Tendency: 

Measures of Central Tendency Mean Can be used in interval and ratio data

Measures of Dispersion: 

Measures of Dispersion Range 60%

Measures of Dispersion: 

Measures of Dispersion How much cleverer am I?

Squaring deviations: 

Squaring deviations 42 = 16 (- 4)2 = 16 Add up all (deviations)2 Number of scores we have (N) = Variance (N-1) used to divide instead of N Field A. (2003) How to Design & Report Experiments’, Sage Publications, London, p129.

Standard Deviation: 

Standard Deviation Push-up squared? Square-root of variance = standard deviation

Presenting our statistics: 

Presenting our statistics The mean number of push-ups for kryptonite drinkers is 5.7 push-ups (S.D. = 3.01) Or, Non-kryptonite drinkers did less number of push-ups (M = 2.0, S.D. = 2.7) than kryptonite drinkers (M = 5.7, S.D. = 3.01).

Presenting our statistics: 

Presenting our statistics Or we could portray this information using a graph, something like this…

Summary: 

Summary Distributions Measures of central tendency Measures of dispersion Using graphs Remember to read the directed reading!