Dot plots are normally used for discrete data. For data sets containing more than data points, dot plots are often inconvenient and other representations are preferred.
Sarah likes the candy Frutty. They are sold in packs of thirty, with the different flavors: apple, orange, and banana. Sarah wanted to know how many banana-flavored candies there are in each pack. She bought ten packs and counted the number of banana bars in each. Her results are as follows. Draw a dot plot to represent the data.
First, we should notice the minimum and maximum values of the data set. It can be seen that they are and respetively. We can draw a horizontal number line for the dot plot from to
Next, we can mark a dot for each data point one by one until all points are marked.
From the dot plot, we can see that several packs had banana-flavored candies and none had
From the histogram, it can be seen that apples weigh between and grams. In a histogram all intervals must have the same size.
If each interval in the histogram has approximately the same frequency it is said to be uniform.
When a histogram has a peak which is not in the middle, the histogram is skewed.
When drawing a histogram, it is necessary to first decide the intervals. Each interval must have the same length and all data points must lie in an interval. Consider the following data set. One method to find a suitable number of intervals is to take the square root of the number of data points. Here that number is Thus, the histogram can have either three or four intervals. Here, it will have four. Next, it is necessary to determine the size of the intervals. Since the lowest data value in the set is and the highest is using four intervals with a range of will encompass all data points. The intervals are then Next it is recommended to make a frequency table showing how many data points lie in each interval.
From the frequency table, the histogram can be constructed by drawing a bar over each interval a height corresponding to the frequency.