Unit 4- StatisticsHW 7C and 7D Due

Wednesday– 30 points

Section 7C- Grouped Quantitative Discrete Data

Grouped Quantitative Discrete Data

O You can group data values if there are many different data values with low frequencies.

O Grouping data class intervalsO You still have a modal class, which means what??O Compare these two Tables:

O Data values: Frequency Table

O Vs

9 10 13 14 15

19 20 21 21 23

25 26 26 27 28

29 30 31 31 32

34 35 36 37 38

41 42 49 55 40

Number of cars

Tally Frequency

Relative frequency—how do we calculate it?

0 to 9 1

10 to 19

5

20 to 29

10

30 to 39

9

40 to 49

4

50 to 59

1

Total 30

Column graph for grouped data is the same

O Just have the intervals on the x-axis

O Most likely you will have grouped intervals for your data.

O How would you group GPA?O How would you group ages of students at GWHS

Stem and Leaf PlotsO Stem and Leaf plots is a method of writing

data in groups without losing information about the actual data value

O For numbers with 2 digitsO The first digit is the STEMO The second digit is the LEAFO So, in the number 27, 2 is the stem and 7 is

the leafO Examples:

Back to Back Stem and Leaf Plots

O A back to back stem and leaf plots allows us to compare sets which are related.

O The example is times for the 100 meter freestyle recorded by members of a swimming team

O Name two descriptions of the data

Done with Exercise 7C, now it’s your turn to complete a question

One partner should complete the Zinc half of a stem and leaf, and the other partner should complete the Lead part

Answers to example 7C

This is how I feel

Section 7D- Quantitative CONTINUOUS Data

O When we measure data that is continuous, we cannot write down an exact value. Instead we write down an approximation which is only as accurate as the measuring device.

O Quantitative Continuous Data is measured using a FREQUENCY HISTOGRAM or just a HISTOGRAM

O There are no gaps between the columnsO And the modal class is the ______ barO **** to choose intervals, us the squareroot of the

number of data points. For large data sets, we use more classes than less****

Done with Exercise 7D, now it’s your turn to complete a question

Answers to Example 7D

Section 7E- Measuring the Centre of Data

O Mean- averageO Mean for entire population is μ muO Mean for sample population is Ë “x bar”

O Median- middle value, or average of the two middle values

O Mode- value that occurs the MOST, there can be two modes

O The calculator will find the mean and median for youO Examples of mean

O The average height of adult females is 5 feet 5 inchesO The average height of adult females in this class is 5 feet

3 inchesO which is the mean for the entire population?O Which is the mean for the sample population?

Find the mean, median, and mode

5 6 8 10 5 6

7 8 9 10 5 5

5 4 8 9 7 10

AnswersO Mean = sum of all data/ number of data= 127/18=7.06

O Median= middle data= 7

O Mode = most frequent data value =there are 5 “5’s”There are three “8’s”There are three “10’s”So, the mode is 5

Find the mean, median, and mode using a calculator

5 6 8 10 5 6

7 8 9 10 5 5

5 4 8 9 7 10

Step 1: put data into the calculator-Stat-Enter, Edit-Clear L1 by highlighting L1 and hitting CLEAR and ENTER-Done, so 2nd Quit

Step 2: have the calculator find the mean and median for you-Stat- Go right, Calc- Enter, for 1-variable Stat- Enter

Done with Exercise 7E- Now it’s your turn to do an Example

Answers to Example 7E

Effects of Outliers…central tendency means mean, median, mode