# Showing standard deviation on a histogram

Here's the histogram: Let me define some stuff first.

Y-axis: number of times reached value on the x-axis

Orange bars: Object #1

Gray bars: Object #2

Right vertical line: mean for object #1, mean = 85.85

Left vertical line: mean for object #2, mean = 63.85

Standard deviation for object #1: 1.5

Standard deviation for object #2: 2.8

Now, most of that data is useless to you guys, but how should I go about representing the standard deviation around each object's mean? The standard deviation has to do with the x-axis by the way.

The reason I ask this question is because of this sentence in one of my books: "Mark the standard deviations around the mean for each object and add a horizontal line to show this for each object."

I thought that these deviations would be other vertical lines, but that sentence says otherwise.

Thanks for any help.

• I presume they are thinking of a horizontal segment, maybe starting at mean minus 1 sd and extending to mean plus 1 sd; drawn just above or below the y=0 line ie horizontal axis. Btw it's "vertical" not "verticle". – Peter Ellis Feb 2 '18 at 2:53
• @PeterEllis I think I see what you mean. For example, mean = 85, sd(+1) = 86, sd(-1) = 84, so now I can draw a line from 84 to 86, and it probably doesn't matter where it is drawn on the y-axis as long as it is defined as sd. Can you make sure what I said is correct? Thank you for your help. – JustHeavy Feb 2 '18 at 3:01