Algebra 1 Common Core Student Edition, Grade 8-9

Pr o b l em 3 Interp reting H ist o g ram s

Where have you seen
sy m m et r y b ef o r e?
The parabolas you
graphed in Chapter 9 are
symmetric w ith respect
to their axis of symmetry.

Is each histogram uniform, symmetric, or skewed?

Q ------------------------------

Interval

This histogram is symmetric because

the halves are close to mirror images.

Interval

This histogram is skewed because

the peak is not in the center.

0 Got It? 3. a. The following set of data shows the numbers of dollars Jay spent on lunch

over the last two weeks. Make a histogram of the data. Is the histogram

uniform, symmetric, or skewed?

17 1 4 11 14 14 5 16 6 5 9 10 13 9

b. Reasoning How much money should Jay plan to bring for lunch next

week? Explain your reasoning.

What does a

cu m u lat iv e f r eq u en cy

table tell you?

A cumulative frequency

table tells you the

number of data values

that are less than or

equal to the upper limit

of each interval.

A cumulat ive frequency t able shows the number of data values that lie in or below

a given interval. For example, if the cumulative frequency for the interval 70-79 is 20,

then there are 20 data values less than or equal to 79.

Pr o b l em 4 Making a Cumulative Frequency Table

Text M essag i ng The numbers of text messages sent on one day by different students

are shown below. What is a cumulative frequency table that represents the data?

1 7 3 1 3 0 1 1 7 1 5 2 3 9 2 2 1 3 2 0 2 1 1 ^ 9 ) 4 1 2 7 2 ^ 0

St e p 1 Daily Text Messaging

St e p 2

Divide the data into

intervals. The minimum

is 0 and the maximum

is 49. You can divide the

data into 5 intervals.

Write the intervals

in the first column.

Record the frequency

of each interval in the

second column.

ber of

essag es Fr eq uency mil

0-9 11

11 n

10-19 (^3) .......... (^14) ...... '
20-29 3 17
..........30-39...............j^219
40-49 221
11 + 3 = 14
14 + 3 = 17
17 + 2 = 19
19 + 2 = 21
St e p 3 For the third column, add the frequency of each interval to the frequencies of
all the previous intervals.
& Got It? 4. What is a cumulative frequency table that represents the data below?
12 13 15 1 5 7 10 9 2 2 7 11 2 1 0 15
734 Ch ap t er 12 Data Analysis and Probability