The Z score
The z-score is a measure of how many standard deviations a data point falls from the mean. Z-scores are typically rounded to 2 decimal places.
The formula for the z-score is (data point - mean)/(standard deviation)
Example of a z-score calculation
Example: Suppose the mean height of students at the college in inches is 57”
Quartiles and Five-Number Summary
Another way to look at the variation or spread of the data is to divide the data set up into quartiles. To do this you must first put the data in ascending order.
The middle number of the data set (we know currently as the median) is the middle quartile or second quartile, often written Q2.
To find the first
Frequency means how often something occurs. A frequency table puts data into a nice readable form of how often a piece of data occurs in the data set. It will also show the percentage. We have two types of percentages shown, relative frequency and cumulative frequency. The relative frequency simply states the % that the particular data poin