I'm having trouble with histograms! I did stats for A level, and as I remember histograms are used to represent continuous variables. We get the data, make some group sizes, find the frequencies and calculate the frequency densities, and make your histogram; X axis has the units of the variable and the Y-axis has frequency density - right?
So when I've come to Uni, we're recapping stats. We get shown some lectures and tolded to use STATA, a stastics program.
Now on this it produces histograms with only frequency up the side, and the units across the bottom.
This means that the areas of the bars no longer reflect the frequency! I mean obviously the class widths are all the same, as they have to be, but surely this defeats the point of a histogram? It's like a bar chart as the height of the bars now are the frequency!
But if my stats lecturer is telling us this, and STATA is producing histograms like this surely it can't be wrong! What type of histograms are these?
Well attached is the picture from one of our online lectures, which is meant to show that the histogram on the right (with 100 samples, with 326 people in each sample) has a reduced spread compared to the one on the left with only 47 people in 100 samples. If you add up the height of all the bars, it adds up to 100 on both - like a bar chart. I'm confused!