How do you normalise a set of numbers in a data set?
Subtract the mean & divide by the standard deviation (SD)
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What are the factors of a normalised set?
Zero mean & unit variance
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What does a normalised value of -2 mean?
The original value was 2 standard deviations (SD) BELOW the mean
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How do you perform normalisation on SPSS?
1. Gather original values in data-set. 2. Calculate descriptive statistics to find the mean & SD 3. On compute variable, take the original data values & minus the mean divided by the SD
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Why are normalised values used?
To understand & easily compare scores
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What is another term for normalised values?
Z-scores
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What are the characteristics of a normal distribution?
Symmetrical around the mean, only one mode, continuous & has tails which approach but never touch the x-axis
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Where is 95% of the data in a normal distribution?
Two standard deviations (SD) away from the mean
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Where is 68% of the data in a normal distribution?
One standard deviation (SD) away from the mean
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Correlation
A statistical relationship between two variables
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Positive correlation
The variables move in the same direction. When one variable increases, so does the other one
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Negative correlation
As one variable increases, the other variable decreases (either positively/negatively)
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