SADC Course in Statistics Taking measurements Module I1, Session 17

To put your footer here go to View > Header and Footer 2 Learning Objectives You should be able to: Explain the parallels between a questionnaire and other types of measurement Recognise the specialised skills needed to collect measurements Appreciate that the data layout and later problems are similar for questionnaires and other measurements

To put your footer here go to View > Header and Footer 3 Activities 1.This presentation 2.Three short videos Collecting information on animals On plants And on insects 3.A crop-cutting survey measuring areas And yields. 4.A practical exercise Taking measurements yourselves

To put your footer here go to View > Header and Footer 4 Body fat and body shape (CAST 1.2.1) Percentage body fat of individuals is an important measure of their health. To determine how body fat is related to other physical characteristics, scientists accurately determined body fat (using an underwater weighing technique) And made several other body measurements from a group of 252 men. The following diagram shows some of these measurements The heights were recorded in inches, The other body measurements were in centimetres!)

To put your footer here go to View > Header and Footer 5 The measurements Height, chest, knee, thigh body fat, age

To put your footer here go to View > Header and Footer 6 The data – ready for analysis

To put your footer here go to View > Header and Footer 7 What can we learn from this? So far in this course Data are mainly from questionnaires Or from participatory studies They have to be carefully prepared And be well administered usually needing special training To produce useful data The responses follow our skills in verbal communication But we can also measure!

To put your footer here go to View > Header and Footer 8 This example Shows physical measurements height, knee circumference, etc body fat And a question on age The data have the same structure whether we question, or measure So data checking (Module I2) and analysis (I3) and presentation (I4) will be similar But we may need special training to take good measurements just as we do to ask questions well

To put your footer here go to View > Header and Footer 9 Types of measurement There are many For example lengthof seed weightof baby timeof a task count of insects, elephant dung blood sugarof people temperatureof the atmosphere distancealong a rope – participatory study The videos (Activity 2) show some examples for insects, animals and plants

To put your footer here go to View > Header and Footer 10 We can ask and measure Often we do both The Swaziland crop cutting survey Has questionnaire data and measures areas of fields and then the yield of the crops particularly maize

To put your footer here go to View > Header and Footer 11 You can measure repeatedly To monitor blood sugar, rainfall, temperature, weight To compare precisely measure before then make a change – e.g. training measure again

To put your footer here go to View > Header and Footer 12 Activity 2 – measuring animals, etc This is described in the practical Watch the 3 short videos Answer the simple questions The first is on measuring insects – tsetsi fly The second on measuring animals The third on measuring plants

To put your footer here go to View > Header and Footer 13 Activity 3: Swaziland crop-cutting This is described in the video The background is in the full video shown in B1 Session5 This video shows just 2 of the sections The following slides outline the forms for recording the area under each crop The practical is for you to discover how to record the yields

To put your footer here go to View > Header and Footer 14 Each enumerator has a copy of this guide Here is how they record the areas under each crop

To put your footer here go to View > Header and Footer 15 Holding layout sketch plan Field 1 Maize Field 2 60% maize, 40% pumpkins Field 4 maize Field 3 beans

To put your footer here go to View > Header and Footer 16 Symbols for the sketch plan

To put your footer here go to View > Header and Footer 17 Field area measurements

To put your footer here go to View > Header and Footer 18 Area in each field 01 Maize 100% M 60% Pk 40% Beans 100% Maize 100%

To put your footer here go to View > Header and Footer 19 Total crop area

To put your footer here go to View > Header and Footer 20 Other information is also recorded

To put your footer here go to View > Header and Footer 21 Plus household information

To put your footer here go to View > Header and Footer 22 Activity 3 continued – measuring yields How do they measure the yields? How large are the plots? How are they sited within the fields? Finding the plots is the task discussed in the practical handout

To put your footer here go to View > Header and Footer 23 Activity 4 – taking measurements Work in pairs One person measures the time taken by the second person to do the exercise and whether the answer was correct Then you swap round This is done twice The exercise is described in the handout –and on the following slides It is from CAST section 3.2.5

To put your footer here go to View > Header and Footer 24 Remember the aim It is to practice a task that involves taking measurements So it is less important that the answers are right But we might as well give a useful exercise so this reviews the standard deviation or it introduces it.

To put your footer here go to View > Header and Footer 25 The first task

To put your footer here go to View > Header and Footer 26 An acceptable answer has a tick

To put your footer here go to View > Header and Footer 27 Same exercise from a different summary

To put your footer here go to View > Header and Footer 28 Not close enough this time

To put your footer here go to View > Header and Footer 29 How to do the questions The standard deviation (s.d.) is a measure of spread of the data –it is a “typical deviation from the middle” Often about 70% of the observations –are within 1s.d. of the mean And most of the observations –are within 2 s.d. of the mean

To put your footer here go to View > Header and Footer 30 My reasoning The mean is about 1000mm Smallest is about 600 and largest about 1400 So the maximum deviation from the mean is about 400 and a “typical deviation” is about 200mm

To put your footer here go to View > Header and Footer 31 With the boxplot Same idea again – maximum deviation is about 250 from the mean So my estimate of 70 was too small The correct value was 138

To put your footer here go to View > Header and Footer 32 The task Design a simple form Record the time for each example And whether the answer was OK The objective of the study is to know whether the task is easier from the histogram, or from the boxplot The results are collected in pairs And can then be accumulated for the class

To put your footer here go to View > Header and Footer 33 Learning Objectives Can you now: Explain the parallels between a questionnaire and other types of measurement Recognise the specialised skills needed to collect measurements Appreciate that the data layout and later problems are similar for questionnaires and other measurements

To put your footer here go to View > Header and Footer 34