Flashcards
Statistics Lecture 3 - Describing Variables Numerically
Flashcards do conjunto (14)
- 1Uses of Descriptive StatisticsEstimates of central tendency:
Provides a good summary of the location of scores on scale
Mean, median, mode
Measures of disperson:
Quantifies how much the scores vary.
Range, variance, inter-quartile range - 2Meanvalue obtained when the scores are added all together then deivided by the number of scores; the average
- 3How means are affected- Means are not always exactly in the middle of a distribution
- Means are affected by outliers and move towards the outlier - 4MedianCentral score once values have been arranged in numericalorder
- 5Comparing Means of Central Tendency
- 6Measures of Dispersion
- 7RangeThe difference between the highest and lowest value
- 8Inter-Quartile RangeIn Psych, usually the middle 50%
- 9How to calculate IQRQ3 - Q1 = IQR
where Q3 is median of Q2 to max
and Q1 is median from min to Q2 - 10VarianceThis focuses on the average amount that each case in the sample differs from the mean
It is an indication of the variability of your data - 11How to generally calculate varianceYou can work out the variance by calculating:
The arithmetic mean
How much each case differs from this mean
Squaring each of these deviations
Summing these squared deviations
Dividing the result by the number of cases - 12Example of standard deviations calculationsVariance = 193/12
16.08
- 13Important things to know about VarianceVariance cannot be interpreted in isolation.
It is dependent on the measure in question:
Wide numerical scale will tend to have large variances, and vice-versa.
Variances are also often reported comparatively
For example, males vs. females. - 14Summary of this TopicWe can describe our sample in terms of central tendency, spread or variability
The mean is the ‘average’ value
The median is the ‘middle’ value
The mode occurs most frequently
The range is the difference between the lowest and the highest value
The inter-quartile range is the range of the central 50% of the sample
Variance assesses the variability of the data
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- University Undergraduate Statistics FlashCards sobre Statistics Lecture 3 - Describing Variables Numerically, criado por sarahderveeuw em 22-04-2015.
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