Day 6 Flashcards
(11 cards)
Frequency distribution graphs
Distributions gives you a picture of central tendency (mean, median. mode)
Measuring variability
Characteristics of a distribution: shape, central tendeccndy, variability, Knowing that the mean is not enough, if you report a mean with no distribution/variability. Stastics is about explaining variability.
Four basic measure of variability
Range, interquartie range, variance, standard deviation.
The range
A rough estimate of variability, the difference between the highest score in a distribution and the lowest score in the distribution with whole numbers (highest x-lowest x) very sensitive to extreme scores.
Interquartile Range
Avoids the problem of extreme scores , finds the scores that defines the middle of a distribution.
Standard Deviation
Most common used mesaure of variabiliy. Average distance from the mean. uses all of the data.
Deviation
Deviation is the difference between a score and the mean of distribution. Sum of the deviation is always zero, deviations are squared first and then added together. divide by N to get the variance, the square root is called the standard deviation.
Definitional Formula
Expresses the process for obtaining a value in mathematical formula.
Representative samples
s a small quantity of something that accurately reflects the larger entity. An example is when a small number of people accurately reflect the members of an entire population.
Degrees of freedom
variability of a sample is limited the limitations is expressed by degrees of freedom. Number of values that are free to vary under some restriction.
Properties of standard deviation
adding a constant to each score does not change the standard deviation. Multiplying each score by a constant causes the SD to be multiplied by the same constant,
