In this lesson we are going to learn about data collection methods including counting, photographing, digging, sample collection and its types
Answer Text: 6. Collecting Samples -Getting a small part e.g. of soil, rock or vegetation to represent the whole to be used to carry out tests in the laboratory. 7. Counting/census taking - Arithmetical counting and recording. 8. Photographing - Capturing on film or video and still photographs. 9. Digging- Using tools such as hoe pick axe, spade or soil auger to get samples of soil and rocks. 10. Feeling and touching - Using fingers to feel the surfaces of soils and rocks to get their textures. 11. Sampling - Examining by taking a sample -a part representing the whole (population). Types of Sampling 1. Random Sampling- Selection of members of a group haphazardly where every item has an equal chance of being selected e.g. to select 5 students to go for a tour from a class: • Class members write their names on pieces of paper • They are folded and put in a basket • The basket is shaken and fives papers are taken out 2. Systematic Sampling-Selection of members of a sample from an evenly distributed phenomena at regular intervals e.g. after every 10 items/members. 3. Stratified sampling -Selection of members of a sample by breaking the population into homogenous groups e.g. to select 6 students to go for a tour: • Break the class into boys and girls• Select 3 student from each group by random or systematic sampling • Combine units from each group to form the required sample. 4. Cluster Sampling -Selection of sample by dividing the sample into clusters with similar characteristics then a sample is taken from each cluster and representative choices from each cluster are combined to form a sample e.g. to sample the housing cost an estate is chosen to represent each group and representative choices are chosen from each estate and combined to form a sample. Advantages a) It’s less expensive b) It saves time c) It avoids bias Disadvantagesa) A poor selected sample can lead to misleading information b) Systematic sampling can only be done to an evenly distributed population Experimentation – Conducting a test or investigation to provide evidence for or against a theory e.g. to determine the chemical composition of rocks and soils. Advantagesa) First hand data is obtained b) Gives accurate results if properly conducted. c) It can lead to further discoveries Disadvantages a) May be expensive as it involves use of expensive equipment. b) May be time consuming c) Use of defective instruments may lead to inaccurate resultsd) Improper handling of equipment and chemicals may lead to accidents
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