In statistics what is an interval on a relative frequency histogram?

Question

In statistics what is an interval on a relative frequency histogram?

Answer 1

I understand the diffuculty of statistics myself and found these websites which may or may not help you find your answer:

http://www-personal.umich.edu/~bobwolfe/503/lectures/2graph/tsld059.htm

http://www.stat.wmich.edu/s216/book/node11.html

Answer 2

"In statistics, a histogram is a graphical display of tabulated frequencies. A histogram is the graphical version of a table which shows what proportion of cases fall into each of several or many specified categories. The categories are usually specified as nonoverlapping intervals of some variable. The categories (bars) must be adjacent." (http://en.wikipedia.org/wiki/Histogram)

e.g. Let's say you wanted to draw a histogram of smokers in your town. On the x-axis you would note the number of cigarettes smoked per day and on the y-axis the number of smokers who smoke that may cigarettes.

Because you don't want to know exactly how many cigarettes every single one of them smokes you create intervals which means. you define groupings on your x-axis: 1-10 cigarettes a day, could be your first interval (you could also give it a name, like: light smokers) now the next interval would start at 11, as the intervals mustn't overlap! so interval 2, could be from 11-20 cigarettes a day (moderate smoker)... interval 3, 21-30 cigarettes (medium-heavy smoker) and interval 4 31-40 cigarettes a day (very heavy smoker).
Now if you would make a survey amongst all the smokers in your town, you could make a frequency distribution for each interval. You would ask them into which group they belong and could show the result of it in a histogram by drawing a bar, above each interval that you have marked on the x-axis, straight up to the height of the y-axis that indicates the number of eacht type of smoker that you have counted. e.g. 15 smokers indicated that they belonged to interval !, you pull the bar up to 15 along your y-axis. 12 are moderate smokers (they smoke between 11 and 20 cigarettes a day) yor draw the bar up to 12.
8 of them are medium-heavy smokers, the bar for the 3rd interval goes to 8 on the y-axis and last but not least there are 5 old, coughing guys who smoke up to 40 cigarettes a day, to indicate the frequency of their interval you pull up the bar to 5.

Answer 3

There's no single answer. Normally what you do is find the range (maximum score - minimum score) and divide by the number of subdivisions you want. So if your scores ranged from 20 - 50 and you wanted 6 categories, you'd take 30 / 6 = 5, and your intervals would count by 5's.

Answer 4

Post the entire data!