Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Chapter 7 Statistics and Probability

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. 7.1 Reading Pictographs, Bar Graphs, Histograms, and Line Graphs

Martin-Gay, Developmental Mathematics, 2e 33 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Reading Pictographs A pictograph is a graph in which pictures or symbols are used. This type of graph contains a key that explains the meaning of the symbol used. Advantage – comparisons can easily be made Disadvantage – hard to tell what fractional part of a symbol is shown

Martin-Gay, Developmental Mathematics, 2e 44 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Example The following pictograph shows the approximate number of spaceflights by various countries or space consortia for lunar or planetary explorations from 1957 to the present day. Use the graph to answer the questions. continued

Martin-Gay, Developmental Mathematics, 2e 55 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. continued a. Approximate the number of space flights by the United States. The United States corresponds to 12 ½ symbols, and each symbol represents 12 ½ · 7 = 87.5 ≈ 87 spaceflights for lunar and planetary exploration. b. Approximate how many more spaceflights were undertaken by the USSR/Russia than by the United States The USSR/Russian shows 16 symbols, or 3 1 /2 more than the U.S. This means that the USSR/Russia undertook 3 ½ · 7 = 24.5 ≈ 24 more spaceflights than the United States.

Martin-Gay, Developmental Mathematics, 2e 66 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Reading and Constructing Bar Graphs A bar graph can appear with vertical bars or horizontal bars. Advantage – the scale is usually included for great accuracy.

Martin-Gay, Developmental Mathematics, 2e 77 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Example The following bar graphs shows the number of endangered species in the United States in Use the graph to answer the questions. continued

Martin-Gay, Developmental Mathematics, 2e 88 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. continued a. Approximate the number of endangered species that are clams. We go to the top of the bar that represents clams. There are approximately 62 clam species that are endangered. b. Which category has the most endangered species? The most endangered species is represented by the tallest bar. The tallest bars correspond to birds and fish.

Martin-Gay, Developmental Mathematics, 2e 99 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Reading and Constructing Histograms A histogram is a special bar graph. The with of each bar represents a range of numbers called a class interval. The height of each bar corresponds to how many times a number in the class interval occurs and is called class frequency. The bars in a histogram lie side by side with no space between them.

Martin-Gay, Developmental Mathematics, 2e 10 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Reading Line Graphs Another common way to display information with a graph is by using a line graph. Advantage – it can be used to visualize relationships between two quantities. It can also show a change over time.

Martin-Gay, Developmental Mathematics, 2e 11 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Example The following line graph shows the average daily temperature for each month for Omaha, Nebraska. Use the graph to answer the questions. continued

Martin-Gay, Developmental Mathematics, 2e 12 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. continued a. During which month is the average daily temperature the highest? This corresponds to the highest point, which is July. b. During what month, from July through December, is the average daily temperature During the month of September, the average daily temperature was c. During what months is the average daily temperature less than These months were January, February, and December.