Week 5 Flashcards
What is Variability?
how much scores differ from each other. Variability is the measure of the difference between scores. Variability tell you how much scores are spread out or clustered together.
What are the three measures of variability ?
range, Variance, and Standard deviation
What are the limitations of Range?
The range is completely determined by the two extreme values and ignores the other scores in the distribution.
Define variance
Variance is the average number that each score deviates from the mean.
Define standard deviation
Measure the average distance from the mean
How can you visually estimate the sd in a frequency distribution?
the standard deviation should not be higher than the range
When should you use the computational formula for sum of squares?
when the mean is not a whole number
How do you account for lower variance in sample statistics?
Samples tend to underestimate the population value. the variability tends to be consistent, so it can be corrected using degrees of freedom. the sample formulas subtract 1 to correct the bias in sample variability, this increases the the number you would get. (Sample variability is higher)
Unbiased statistic
the average value of the statistic is equal to the population parameter
Biased statistic
the value of the statistic over or under estimates the population parameter
How does adding or subtracting a constant from each score effect the SD and mean
- doesn’t change the SD
* changes the mean by that constant
What is the effect on SD: multiplying or dividing each score by a constant.
standard deviation to be multiplied by the same constant
Low variability means…
existing patterns can be seen clearly
High variability means…
can obscure patterns in the data and, therefore, can create a problem for inferential statistics
What is central tendency?
using an average or typical value to provide a simple description of the entire sample. y can describe an entire distribution and make comparison between groups of individuals or sets of data.
