Chapter 8 - Statistics

• Wiskunde
• Middelbare school
• havo
• Leerjaar 3

Mean, Mode and Median

The number of times a value occurs is called the frequency.

The value with the highest frequency is called the mode.

When none of the values has the highest frequency there is no mode.

When a series of values is ordered from small to large, the middle value is the median.

When there is an even number of values the median is the mean of the two middle values.

Absolute and Relative

Absolute frequencies are the actual numbers.

Relative frequencies are ratio numbers e.g. percentages.

When the relative frequencies decrease(increase) , it does not automatically mean that the absolute frequencies decrease(increase).

Grouping Data

Why do we need to group data?

To get a clear overview of the data.

Keywords:

Class Interval 

Midpoint of a class

modal class

You need to know: How to calculate the mean of grouped data.

Measures of Spread

A measure of spread is the range

The range is the difference between the highest and lowest value.

The median of the first half of values arranged in ascending order, is called the lower quartile.

The median of the second half is called the upper quartile.

The median and the quartiles divide a series of values in four groups.

Another measure of spread is the interquartile range.

This is the difference between the upper and lower quartiles.

Box Plot

Tekst

What do you need to know to draw a box plot

• lowest number
• Highest number
• Median
• Lower quartile
• Upper quartile

Representing Data

Data, collected in a survey, can be represented in different ways, for example in a bar chart, a box plot, a pie chart or as grouped data.

You can represent data in a scatter graph. In a scatter graph you can see if there is any correlation (connection) between the sets of data it represents.

What you need to know

• Grouped data, midpoint of a class and modal class
  
• You can calculate absolute and relative frequencies
• You can calculate the mean of grouped data
• You can calculate the range, the quartiles and the interquartile range
• You can read off the data from a box plot
• You can draw a box plot 
• You can interpret different representations of data