Notes Unit 8: Dot Plots and Histograms

Transcription

1 Notes Unit : Dot Plots and Histograms I. Dot Plots A. Definition A data display in which each data item is shown as a dot above a number line In a dot plot a cluster shows where a group of data points fall. A gap is an interval where there are no data items.

2 B. Steps to Create a Dot Plot 1. Order numbers from least to greatest. 2. Draw a number line, labeling the number line with the minimum and the maximum and then all the numbers that fall between them. 3. Put a dot above each number on the number line for each data entry in your set. Don t forget a title and labels!

3 C. Examples Ex 1: A. In an airline training program, the students are given a test in which they are given a set of tasks and the time it takes them to complete the tasks is measured. The following is a list of the time (in seconds) for a group of new trainees. 61, 61, 64, 67, 70, 71, 71, 71, 72, 73, 74, 74, 75, 77, 79, 0, 1, 1, 3 Display the data in a dot plot.

4 Answer! Airline Training Program Test New Trainees = 1 person Time in Seconds

5 Are there any clusters? = 1 person Airline Training Program Test New Trainees Yes! Time in Seconds

6 Are there any gaps? Airline Training Program Test New Trainees Yes! = 1 person Time in Seconds

7 What is the average time? = 1 person Airline Training Program Test New Trainees About 73 seconds Time in Seconds

8 What is the median time? = 1 person Airline Training Program Test New Trainees 73 seconds Time in Seconds

9 What is the Range? = 1 person Airline Training Program Test New Trainees 22 seconds Time in Seconds

10 Ex 2: B. In a science class, the students weighed some samples of dirt to the nearest 1/ pound. The weights of the samples are given below. 1/ lb, 3/ lb, ¾ lb, ¼ lb, 1/ lb, ¼ lb, 7/ lb, ¼ lb, 3/ lb, ¼ lb, ½ lb, 3/ lb Make a dot plot for the data.

11 Answer! Sample Weights = 1 sample Weight in pounds

12 Are there any clusters? Sample Weights = 1 sample Yes! Weight in pounds

13 Are there any Gaps? Sample Weights = 1 sample Yes! Weight in pounds

14 What is the average weight? Sample Weights = 1 sample 3/ or lb Weight in pounds

15 What is the median? Sample Weights = 1 sample 5/16 or lb Weight in pounds

16 What is the range? Sample Weights = 1 sample 6/ or 0.75 lb Weight in pounds

17 You try: Mrs. Jones took a survey of ten 6 th grade students. She asked each student how many items they recycle in a day. Below are her results. 0, 1, 1, 1, 2, 2, 2, 3, 3, 5 Make a dot plot to display this data.

18 II. Bar Graphs and Histograms A. Bar Graphs A bar graph can be used to display and compare data The scale should include all the data values and be easily divided into equal intervals.

19 How to interpret a Bar Graph? The bar graph shows Mr. Snow s students by gender How many of Mr. Snow s students are band members? How many of Mr. Snow s students are not band members? and band membership. Snow s Students by Gender & Band Membership

20 B. Double Bar Graph Can be used to compare two related sets of data 1st Qtr 2nd Qtr 3rd Qtr 4th Qtr How to make a Double-Bar Graph? 1. Choose a scale and interval for the vertical axis. 2. Draw a pair of bars for each variable. If possible, use different colors. 3. Label the axes and give the graph a title. 4. Make a key to show what each bar represents.

21 Ex 1: The table shows the highway speed limits on interstate roads within three states. State Urban Rural Florida 65mi/h 70 mi/h Texas 70 mi/h 70 mi/h Vermont 55mi/h 65 mi/h

22 Choose a scale and interval for the vertical axis. Step 1 State Florida Texas Vermont Urban 65mi/h 70 mi/h 55mi/h Rural 70 mi/h 70 mi/h 65 mi/h

23 Draw Step a pair of 2 bars for each state s data. Use different colors to show urban and rural. State Florida Texas Vermont Urban 65mi/h 70 mi/h 55mi/h Rural 70 mi/h 70 mi/h 65 mi/h

24 Speed Limit (mi/h) Step 3 and 4 Speed Limit on Interstate Roads Label the axes and give the graph a title. Make a key to show what each bar represents Urban Rural

25 C. Histogram Histogram is a bar graph that shows the frequency of data within equal intervals. There is no space in between the bars.

26 a. Creating a histogram? Make a frequency table of the data. Be sure to use equal intervals Step 1 Number of hours of TV Number of hours of TV Frequency II IIII IIII - IIII IIII - I III IIII - IIII III IIII IIII - III

27 Step 2 Choose an appropriate scale and interval for the vertical axis. The greatest value on the scale should be at least as great as the greatest frequency. Number of hours of TV Frequency

28 Step 3 Draw a bar for each interval. The height of the bar is the frequency for that interval. Bars must touch but not overlap. Label the axes and give the graph title Number of hours of TV Frequency

29

30 Can you now make a bar graph, double bar Graph and a histogram?

31 You try: The list below shows the results of a typing test in words per minute. Make a histogram of the data. 62, 55, 6, 47, 50, 41, 62, 39, 54, 70, 56, 70, 56, 47, 71, 55, 60, 42