Handling Data Grouped Data

Handling data: grouped data
BTEOTSSSBAT:
Find the mean from grouped data

Grouped frequency tables
Grouped frequency tables are used when a lot of data has to be recorded.
Example
The problem that we have here is that we cannot multiply 2  0-400.

Grouped frequency tables
Grouped frequency tables are used when a lot of data has to be recorded.
Example
The problem that we have here is that we cannot multiply 2  0-400.
To find the midpoint
add the first and last value and divide by 2:

To find the number of hours we need to multiply the midpoint by the no of bulbs
= fx

To find the mean number of hours we need to divide the total number of hours (19200) by the total number of bulbs (20)

= 960 hours

Now try these
1. Andrew did a survey at the seaside for his science coursework.
He measured the lengths of 55 pieces of seaweed.
The results of the survey are shown in the table.
Andrew needs to calculate an estimate for the mean length of the pieces of seaweed.
Work out an estimate for the mean length of the piece of seaweed.

2. A set of 25 times in seconds is recorded.
(a) Complete the frequency table below, using intervals of 5 seconds.
(b) Write down the modal class interval.
(c) Calculate the mean time.

Now try these: Answers
1. Andrew did a survey at the seaside for his science coursework.
He measured the lengths of 55 pieces of seaweed.
The results of the survey are shown in the table.
Andrew needs to calculate an estimate for the mean length of the pieces of seaweed.
Work out an estimate for the mean length of the piece of seaweed.
2830/ 55 = 51.5 (3 sf)

2. A set of 25 times in seconds is recorded.
(a) Complete the frequency table below, using intervals of 5 seconds.
(b) Write down the modal class interval.
(c) Calculate the mean time.
10 t < 15