Histograms & Comparing Graphs

What are Histograms? A histogram is a graphical display of data using bars of different heights. Each bar represents the frequency of an event occurring in an equal sized interval. Histograms are used to analyze large sets of quantitative data. Frequency of

Shapes of Histograms What do you notice about the possible shapes of histograms compared to the possible shapes of dot plots?

How to make a histogram: Determine the range of your data. Lowest number 44. Highest number 72. Range = 28 Determine appropriate equal intervals. 5 numbers per interval. Make a frequency table with the intervals. Put a tally mark in the appropriate interval for each number in your data. Verify that you have the same number of tally marks as you have items of data. Daily high temperatures in degrees Fahrenheit: 63 70 64 71 71 62 68 67 68 72 65 62 59 58 60 59 56 53 51 55 56 50 53 57 55 50 46 49 46 52 48 44 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I

How to make a histogram: Create a graph. Label the x- axis with the intervals from the frequency table. Label the y- axis “Frequency.” Draw each bar to the appropriate height. The bars must touch each other, no gaps between bars unless there are no data points for that interval. F R E Q U N C Y Temperature

Comparing Graphs The dot plot shows the ages of people who are grandparents living in the Aprende neighborhood. How does a dot plot compare to a histogram? When is it better to use a dot plot?

Comparing Graphs Box plots can be created side by side to compare two sets of data on the same scale. This box plot shows average monthly rainfall for Miami, FL and New Orleans, LA. Which city shows a greater range in average monthly rainfall? Explain how the parallel box plots makes it easy to compare the ranges in this case. How do the maximums, minimums, and the medians of the two data sets compare?

Comparing Graphs The test scores of students in a math class are as follows: 80, 72, 82, 80, 80, 80, 88, 88, 84, 92, 92, 96, 70, 90, 98, 92, 88, 92, 90, 80, 84 Which graph is best for finding out the most common test score? Which graph is best if you want to know how many people scored a B on the test? Which graph is best for a teacher who wants to know the range of scores for the bottom 25%, the middle 50% and the top 25%?