# Biostats Chapter Two

## Terms

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- frequency distribution
- lists data calues (either individually or by groups of intervals), along with their corresponding frequencies (or counts)
- lower class limits
- smallest numbers that can belong to the different classes
- upper class limits
- largest numbers that belong to the different classes
- class boundaries
- numbers used to seperate classes, but without the gaps created by class limits. they are obtained as follows: find the size of the gap between the upper class limit of one class and the lower classe limit of the next class, add half of that amount to each upper class limit to find the upper class boundaries and subtract half that amount from each lower class limit to find the lower class boundaries
- class midpoints
- midpoints of the classes, each class midpoint can be found by adding the lower class limit to the upper class limit and dividing the sum by two
- class width
- difference between two consecutive lower class limits or two consecutive lower class boundaries
- histogram
- bar graph in which horizontal scale represents calsses of data values and the vertical scale represents frequencies, the heights of the bars are drawn adjacent to each other (without gaps)
- measure of center
- a value at the center of middle of a data set
- arithmetic mean
- measure of the center found by adding the values and dividing the total by the number of values
- median
- measure of the center that is the middle value when the original data values are arranged in order of increasing (or decreasing) magnitude
- mode
- value that occurs most frequently
- bimodal
- two values occur iwth the same greatest frequency
- multimodal
- more than two values occur with the same greatest frequency, each is a mode
- midrange
- measure of the center that is the value midway between the highest and lowest values inthe original data set, found by adding the highest data value to the lowerst data value and then dividing the sum by two
- skewed
- distribution of data is skewed if it is not symmetric and extends more to one side than the other
- range
- the difference in a set of data between the maximum and minimum value
- standard of deviation
- measure of the variation of values about the mean, it is a type of average deviation of values from the mean that is calculated
- variance
- measure of variation equal to the square of the standard deviation
- sample variance
- square of the standard deviation s
- population variance
- square of the popluation standard deviation sigma
- standardized score
- z score-numer of standard deviations that a given value x is above or below the mean
- 5-number summary
- consists of the minimum value, the first quartile (Q1), the median (or second quartile Q2), the third quartile (Q3), and the maximum value
- boxplot
- box and whisker digram-graph of a data set that consists of a line extending from the minimum value to the maximum value, and a box with lines drawn at the first quartile, median and third quartile