Everyday maths for Health and Social Care and Education Support 1
Everyday maths for Health and Social Care and Education Support 1

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Everyday maths for Health and Social Care and Education Support 1

7.1 Advantages and disadvantages of using the arithmetical average

What are the advantages and disadvantages of using the arithmetical average?

Ever heard of families with 2.4 children? This is the national average but it means nothing – because you can’t have 0.4 of a child! This highlights one of the problems with averages: the value you get may not be a real value in terms of what you are talking about.

Another problem is that the average value will be affected by the highest and lowest values. For example, the NHS recommends not regularly drinking more than 14 units of alcohol per week to minimise the risk of developing an alcohol-related illness. This is an average of 2 units per day. This average would be the same for both, a person who drinks 2 units each day of the week and a person who only drinks on one day each week, but consumes 14 units on this one day. The averages are the same, and it looks like each person is sticking to the guidelines to stay healthy, but in fact the second person will be at higher risk of developing an alcohol related illness as they are binge drinking every week.

Averages are good, however, because they aren’t too complicated to work out (compared to some other statistical calculations) and they use all the available data.

Now try the following activity. Remember to refer to the example if you get stuck and to check your answers once you have completed the questions.

Activity 11: Finding out averages

  1. The ages of four children in a foster family are 4, 6, 8 and 10 years. What is the average age?
  2. Find the average of the following data sets:
    • a.4, 6, 11
    • b.3, 7, 8, 4, 8
    • c.8, 9, 10, 9, 4, 2
    • d.11, 12, 13, 14, 15, 16
  3. A group of friends go out for a meal and some drinks one Friday night. The table below shows the number of units of alcohol consumed by each person:
23013
23213
  • Work out the average number of alcohol units consumed.

Answer

Check your answers with the answers below.

  1. First, add all of the ages together:
    • 4 + 6 + 8 + 10 = 28

    Then divide this total by the amount of data given:

    • 28 ÷ 4 = 7

    The average age is 7.

  2. You will find the following answers using the same calculation you used for question 1:
    • a.Add all the numbers (4 + 6 + 11 = 21) and then divide this answer by the amount of data given (21 ÷ 3 = 7). The answer is 7.
    • b.Add all the numbers (3 + 7 + 8 + 4 + 8 = 30) and then divide this answer by the amount of data given (30 ÷ 5 = 6). The answer is 6.
    • c.Add all the numbers (8 + 9 + 10 + 9 + 4 + 2 = 42) and then divide this answer by the amount of data given (42 ÷ 6 = 7). The answer is 7.
    • d.Add all the numbers (11 + 12 + 13 + 14 + 15 + 16 = 81) and then divide this answer by the amount of data given (81 ÷ 6 = 13.5). The answer is 13.5.
  3. The average number of alcohol units consumed per person is 2:

    2 + 3 + 1 + 3 + 2 + 3 + 2 + 1 + 3 = 20

    20 ÷ 10 = 2

Now have a go at another activity to check your knowledge.

Activity 12: The maths test

  1. In a maths class the scores for a test (out of 10) were as follows:
5 66 4 4
7 3 5 6 7
8 6 2 8 5
4 5 6 5 6
  • What is the average score?
  1. Some of the students felt that the teacher had been too harsh with their marks. The tests were remarked and the new results were as follows:
4 6 6 4 4
6 1 5 6 6
7 6 1 9 5
3 5 6 5 5
  • Work out the average score for these new results. Which set of results gave the best marks? Was the teacher harsh with the first marking?

Answer

  1. First, add up the total number of marks:

    • 5 + 6 + 6 + 4 + 4 + 7 + 3 + 5 + 6 + 7 + 8 + 6 + 2 + 8 + 5 + 4 + 5 + 6 + 5 + 6 = 108

    Then divide this by the number of scores (or the number of students), which is 20:

    • 108 ÷ 20 = 5.4

    So the average score is 5.4 out of 10.

  2. Again, first add up the total number of marks:

    • 4 + 6 + 6 + 4 + 4 + 6 + 1 + 5 + 6 + 6 + 7 + 6 + 1 + 9 + 5 + 3 + 5 + 6 + 5 + 5 = 100

    Then divide this total by 20:

    • 100 ÷ 20 = 5

    The best set of results was the first set. The teacher had not been marking it harshly.

Summary

In this section you have:

  • learned that the mean is one sort of average
  • learned that the mean is worked out by adding up the items and dividing by the number of items
  • understood that the mean can give a ‘distorted average’ if one or two values are much higher or lower than the other values.
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