2Tvwo § 2.6 Grouping data '19'20

• Wiskunde
• Middelbare school
• havo, vwo
• Leerjaar 2

§2.6 Grouping data

Grouping data

If you try to put the data below into a frequency table, you will get a very large table, with a lot of frequencies of 0 and 1. 

To get a more useful frequency table,

you can group data.

Grouping data

Instead of counting the frequency of every separate value, you make groups of values, called class intervals.

Each class interval is the same size

Notice that 7.0 belongs in

the class interval from 7 to 8,

NOT from 6 to 7.

Modal class

When you have a frequency table with

grouped data, you do not talk about the

mode, but about the modal class.

This is the class interval with the

highest frequency.

Here the modal class is from 7 to 8.

Midpoint

To calculate the mean from a frequency table with grouped data, you first calculate the midpoints of each group. This is the mean of the class boundaries.

midpoint from 3 to 4: (3 + 4)/2 = 3.5

midpoint from 4 to 5: (4 +5)/2 = 3.5

etc.

Do you know what 'dirty data' means?

It is WRONG INFORMATION.

See next slide for more!

Mean

Calculating the mean from a frequency table with grouped data is very similar to the method for a normal frequency table.

- multiply the frequency with the midpoint for each class interval

- add up the results and add up the frequencies

- divide the total of the multiplications by the total of the frequencies

Mean

Doing a chapter on Statistics ...

asks a certain TEMPO from you,

dealing with many data in one way or other!

Most tasks are not that difficult,

but just a lot of work.

So: work on your tempo!

Homework

• Make the exercises from your chosen path of §2.6:

- Support: 32, S33, 34, S35, 35, 36

- Standard: 32, 33, 34, 35, 36, 37

- Challenge: 32, 33, 34, 36, 37, C8

• Correct your answers with a red pen