Histogram help

lillybeth

lillybeth

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Nov 1, 2012
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hey, i have a question about histograms, i know how to make a stem-and-leaf plot, but i'm not so sure how to make a histogram. is it anything like a bar graph? can someone explain histograms to me? thanks! :)
 
lillybeth said:
hey, i have a question about histograms, i know how to make a stem-and-leaf plot, but i'm not so sure how to make a histogram. is it anything like a bar graph? can someone explain histograms to me? thanks! :)
Click to expand...
Histograms look like bar charts, but technically they differ. Here is a site on histograms that links to a site on bar graphs. http://www.mathsisfun.com/data/histograms.html Take a look at them. If you still have questions after looking at those sites, come back to follow up. What might be best is to take a problem and try it. Then we can see where you are going wrong if you are.
 
lillybeth said:
so is the difference just the way it's presented?
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No, the difference in presentation represents an important but subtle difference in meaning.
.
The bar chart shows the numbers in two or more distinct categories, like cats, dogs, rabbits, and hamsters. The bars are separated to show that each refers to a different type of thing.
.
The histogram shows the numbers in two or more contiguous ranges of measurements of the same category. The ranges might be under 100 pounds, at least 100 pounds but less than 150 pounds, at least 150 pounds but less than 200 pounds, and at least 200 pounds. Each bar of the histogram shows the number in the given range, but all the bars involve the same unit, namely pounds. So the bars are contiguous to show that the ranges are numerically contiguous and involve the same type of measurement.
 
The following set of numbers represents the number of hours a group of students spent reading over the course of two weeks.
3, 19, 11, 29, 4, 6, 10, 16, 2, 21, 15, 22, 13, 9, 1, 17, 2, 26, 18, 7
On your own sheet of paper, graph the set on a histogram, using six intervals in the display. Make sure to label your graph.



I'm trying to find how to do the above, and can you tell me how to label what I circled in the photo?
Capture.jpg
how do you know how to label the histogram?
 

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lillybeth said:
The following set of numbers represents the number of hours a group of students spent reading over the course of two weeks.
3, 19, 11, 29, 4, 6, 10, 16, 2, 21, 15, 22, 13, 9, 1, 17, 2, 26, 18, 7
On your own sheet of paper, graph the set on a histogram, using six intervals in the display. Make sure to label your graph.



I'm trying to find how to do the above, and can you tell me how to label what I circled in the photo?
View attachment 2698
how do you know how to label the histogram?
Click to expand...
In your problem, what type of measurements are you describing: it is not miles per gallon.
 
lillybeth said:
The following set of numbers represents the number of hours a group of students spent reading over the course of two weeks.
3, 19, 11, 29, 4, 6, 10, 16, 2, 21, 15, 22, 13, 9, 1, 17, 2, 26, 18, 7
On your own sheet of paper, graph the set on a histogram, using six intervals in the display. Make sure to label your graph.



I'm trying to find how to do the above, and can you tell me how to label what I circled in the photo?
View attachment 2698
how do you know how to label the histogram?
Click to expand...
You have freedom to make the histogram bins anything you want. BUT if you have too many bins, many will be empty, OR if you have too few bins, you lose precision.

Here is a rule of thumb: at the minimum, try to make the average counts per bin at least 5. Or if you have lots of data, try to make the smallest number in any bin at least 5.

In this problem, you have exactly 20 data, so having 4 bins would be good, or at most 5. The smallest datum is 1 and the largest is 29, so a scale from 0 to 30 makes sense. 30 is not divisible by 4, but it is divisible by 5. Five bins would be 0-6, 7-12, . . .

HOLD ON!!!
The problem explicitly states to use 6 intervals!!!
What is 30÷6 ?
 
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DrPhil said:
You have freedom to make the histogram bins anything you want. BUT if you have too many bins, many will be empty, OR if you have too few bins, you lose precision.

Here is a rule of thumb: at the minimum, try to make the average counts per bin at least 5. Or if you have lots of data, try to make the smallest number in any bin at least 5.

In this problem, you have exactly 20 data, so having 4 bins would be good, or at most 5. The smallest datum is 1 and the largest is 29, so a scale from 0 to 30 makes sense. 30 is not divisible by 4, but it is divisible by 5. Five bins would be 0-6, 7-12, . . .

HOLD ON!!!
The problem explicitly states to use 6 intervals!!!
What is 30÷6 ?
Click to expand...
5
 
DrPhil said:
"Interval" is a word that can be found in any dictionary. I strongly suspect it can also be found in the discussion of "histogram" in your text.
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i know it was in my problem, but i didn't know what it meant.
interval-the distance between numbers on a graph or data display
i looked it up. soooooo should I have 5 or 6 bins?
 
lillybeth said:
i know it was in my problem, but i didn't know what it meant.
interval-the distance between numbers on a graph or data display
i looked it up. soooooo should I have 5 or 6 bins?
Click to expand...
The base of each bar is an interval along the number line so you would have six bars or bins. The natural way to number them would 0-4, 5-9, 10-14, 15-19, 20-24, and 25-29. As Dr Phil has already pointed out the range 0 to 29 is sufficient to permit you to show all of your data. 0 through 29 is 30 numbers. With 6 bins or bars, you get a nice round number when dividing 6 into 30.
 
ok, so what you do is count how many in each group, like
(0-4) = 5
(5-9) = 2
etc.
then you make that into a graph, using a bar to interpret how many in each group?
am I correct or confused?
 
lillybeth said:
ok, so what you do is count how many in each group, like
(0-4) = 5 VERY GOOD. There is one instance of 1 hour, two instances of 2 hours, one instance of 3 hours, and one instance of 4 hours. When you add up one instance, two instances, one instance, and one instance, that is five instances in the range of 0 through 4, at least in Pennsylvania (I have never tried counting in Kansas.).
(5-9) = 2 Hmm. I see one instance of 6, one instance of 7, and one instance of 9 so when I add those up I think I get three instances in the range 5 through 9. Maybe things are different in Kansas.
etc.
then you make that into a graph, using a bar to interpret how many in each group?
am I correct or confused?
Click to expand...
You have the basic idea. Just be careful with the mechanics.
 
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