sampling............................pptx

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1. RANDOM SAMPLING

2. Learning Competencies The learner will be able to: 1. Calculate the sample size using the Slovin’s formula. 2. Illustrate random sampling.

3. ORAL EXERCISES Describe each of the following. Interview method Questionnaire method Observation method Test method Registration method Experimental method Text method Mechanical devices

4. METHODS OF COLLECTING DATA INTERVIEW METHOD The researcher makes direct and personal contact with the interviewee. The researcher gathers data by asking the interviewee series of questions.

5. INTERVIEW METHOD DIRECT METHOD The researcher personally interviews the respondents. INDIRECT METHOD The researcher uses a telephone to interview the respondents.

6. METHODS OF COLLECTING DATA QUESTIONNAIRE METHOD The researcher distributes the questionnaires either personally or by mail and collects them by the same process.

7. QUESTIONNAIRE METHOD GUIDED-RESPONSE TYPE RECALL TYPE RECOGNITION TYPE DICHOTOMOUS TYPE MULTIPLE-CHOICE TYPE MULTIPLE-RESPONSE TYPE FREE-RESPONSE TYPE RATING SCALE TYPE

8. METHODS OF COLLECTING DATA OBSERVATION METHOD The researcher may observe subjects individually or group of individuals to obtain data and information related to the objectives of the investigation. It is a method of obtaining data by seeing, hearing, testing, touching and smelling.

9. METHODS OF COLLECTING DATA TEST METHOD This method is widely used in psychological research and psychiatry. Standard tests are used because of their validity, reliability and usability.

10. METHODS OF COLLECTING DATA REGISTRATION METHOD This method of collecting data is governed by our existing laws.

11. METHODS OF COLLECTING DATA EXPERIMENTAL METHOD This method of collecting data is used to find out the cause and effect relationship of certain phenomena under controlled conditions.

12. METHODS OF COLLECTING DATA TEXT METHOD The researcher may ask or invite individuals to send text opinions on certain issues or send in their choices on their brand preferences on a particular product using their cellphones .

13. METHODS OF COLLECTING DATA MECHANICAL DEVICES The devices that can be used when gathering data for social and educational researchers are the camera, projector, videotape, tape recorder, etc.

14. SAMPLING It is the process or technique of selecting a representative sample from the entire population. It is a method used to determine which element is to be included in the sample. POPULATION – refers to the entire group of individuals or objects known to have similar characteristics. SAMPLE – is a subset of the entire population.

15. DETERMINING THE SAMPLE SIZE We use Slovin’s formula to determine the statistically acceptable sample size to be extracted from the given population. The Slovin’s formula is where: n = number of samples needed N = population size e = margin of error  

16. EXAMPLE 1. A group of researchers was tasked by the House of Representatives to survey whether students in Metro Manila favor the moving of the start of classes from June to September. If there are 1,000,000 students and 10% margin of error is expected, compute the sample size.

17. EXAMPLE 2. A researcher wants to know the average of the families living in Barangay A which has 2,500 residents. Calculate the sample size the researcher will need if a 5% margin of error is allowed.

18. EXAMPLE 3. A researcher wants to study the effects of social media on Grade 11 students in Pulung Santol National High School. If there are 250 Grade 11 students in the school, how many students should there be in his sample if 5% margin of error is allowed?

19. ACTIVITY 15 Using the Slovin’s formula, determine the sample size given the population (N) and the margin of error (e). 1. N=800 e=2% 6. N=75,000 e=6% 2. N=2,000 e=3% 7. N=20,000 e=4% 3. N=10,000 e=5% 8. N=45,000 e=8% 4. N=50,000 e=7% 9. N=30,000 e=9% 5. N=25,000 e=10% 10. N=15,000 e=5%

20. RANDOM SAMPLING TECHNIQUE or PROBABILITY SAMPLING TECHNIQUE It is a part of sampling technique in which each sample has an equal chance of being chosen.

21. RANDOM SAMPLING TECHNIQUE or PROBABILITY SAMPLING TECHNIQUE It is one of the simplest forms of collecting data from the total population.

22. RANDOM SAMPLING TECHNIQUE or PROBABILITY SAMPLING TECHNIQUE In order to obtain a genuine or unbiased sample, each member of the population must have an equal chance of being included in the sample.

23. RANDOM SAMPLING TECHNIQUE or PROBABILITY SAMPLING TECHNIQUE 1. SIMPLE RANDOM SAMPLING It is the most commonly used random sampling technique. In this technique, each member of the population has an equal chance to be selected as a participant.

24. SIMPLE RANDOM SAMPLING LOTTERY METHOD It is the most primitive and mechanical example of simple random sampling procedure. This is commonly known as the “fish bowl method”.

25. SIMPLE RANDOM SAMPLING LOTTERY METHOD Steps: List down or write the names of each member of the population in a separate pieces of paper. Fold each piece of papers and place in a bowl. Mix and pick. The names to be randomly picked from the bowl will form the sample group.

26. LOTTERY METHOD SIMPLE RANDOM SAMPLING without REPLACEMENT The selection of elements depends entirely on chance. SIMPLE RANDOM SAMPLING with REPLACEMENT This gives an element of the population more than one chance to be a part of the sample and thus, making elements of sample not distinct with one another.

27. SIMPLE RANDOM SAMPLING TABLE OF RANDOM NUMBERS It is a list of numbers that can be used to generate numbers to stimulate experiments.

28. SIMPLE RANDOM SAMPLING RANDOM NUMBER TABLE Steps: Assign numbers to each member of the population. Choose a table number randomly. With eyes closed and pencil or pen at hand, choose the set of numbers from which to start. The number of digits to be considered in the random numbers selected depends on the number of digits needed. Repeat the process until you reach the desired number of members in the sample.

29. RANDOM SAMPLING TECHNIQUE or PROBABILITY SAMPLING TECHNIQUE 2. SYSTEMATIC RANDOM SAMPLING It is a random sampling technique which considers every element of the population in the sample with the selected random starting point for the first members.  

30. SYSTEMATIC RANDOM SAMPLING Steps: Assign numbers to each member of the population. Choose a random starting point. Do this by dividing the number of members in the population by the desired number of samples. The quotient (k) will represent the first (k) member of the population and the random starting point will be determined by the lottery method. From a student number, skip count by k repeatedly until the desired number of samples is completed.

31. SYSTEMATIC RANDOM SAMPLING Systematic sampling is a random sampling technique in which every element of the population is selected until the desired number of elements in the sample is obtained. The value of is calculated by dividing the number of elements in the desired sample. The value of is the sampling interval.  

32. EXAMPLE 1. In a group of 250 students, how will you select a sample containing 71 students by using the systematic sampling technique? 1, 2, 3, 4 , 5, 6, 7, 8 , 9, 10, 11, 12 , 13, 14, 15, 16 , 17, 18, 19, 20 , 21, 22, 23, 24 , 25, 26, 27, 28 , 29, 30, 31, 32 , 33, 34, 35, 36 , 37, 38, 39, 40 , …, 250  

33. EXAMPLE 2. In a group 180 workers, how will you select a sample of 36 workers by using the systematic sampling technique? 1, 2, 3, 4, 5 , 6, 7, 8, 9, 10 , 11, 12, 13, 14, 15 , 16, 17, 18, 19, 20 , 21, 22, 23, 24, 25 , 26, 27, 28, 29, 30 , 31, 32, 33, 34, 35 , 36, 37, 38, 39, 40 , …, 180  

34. EXAMPLE 3. The office clerk gave a researcher a list of 500 Grade 10 students. The researcher selected every 20 th name on the list. How many respondents that the researcher will have? 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 , 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 , …, 500  

35. ACTIVITY 16 Identify the sampling interval and list the assigned number of respondents for the given data. N=30 n=6 N=20 n=4 N=25 n=5 N=35 n=7 N=40 n=10

36. RANDOM SAMPLING TECHNIQUE or PROBABILITY SAMPLING TECHNIQUE 3. STRATIFIED RANDOM SAMPLING It is a random sampling technique, which purposively divides a given population into homogenous partitions called strata.  

37. STRATIFIED RANDOM SAMPLING Steps: Divide the population into smaller subgroups or strata based on the numbers’ shared attribute and characteristics. Compute for the number of sample per strata by dividing the total size per stratum by the total population. Multiply the proportion to the total sample size. Randomly select the members of the sample from each group using either lottery method or table of random numbers.

38. EXAMPLE 1. You want to interview 200 students in your school to determine their opinion on the new school uniform. How are you going to choose your sample by using stratified sampling if there are 1,200 students in Grade 7, 1,100 in Grade 8, 1,050 in Grade 9, 940 in Grade 10, 900 in Grade 11 and 810 in Grade 12?

39. SOLUTION GRADE LEVEL STRATUM SIZE SAMPLE SIZE 7 1200 40 8 1100 37 9 1050 35 10 940 31 11 900 30 12 810 27 TOTAL 6000 200  

40. EXAMPLE 2. Marcela, a Statistics student, wants to determine who care more about their physical appearances, the male or female students. She wants to limit her study to the Grade 10 students. There are unequal numbers of Grade 10 students: 340 are male and 500 are female. She wants her sample to consist only of 50 students. She chooses the members of her sample using stratified sampling technique.

41. SOLUTION GRADE 10 STRATUM SIZE SAMPLE SIZE MALE 340 20 FEMALE 500 30 TOTAL 840 50  

42. EXAMPLE 3. Suppose a researcher wants to determine the average income of the families in a barangay having 3,000 families, distributed in five purok’s . Compute the sample size at a 5% margin of error and identify the number of respondents per purok if there are 800 families in Purok 1, 400 in Purok 2, 500 in Purok 3, 600 in Purok 4 and 700 in Purok 5.

43. SOLUTION PUROK STRATUM SIZE SAMPLE SIZE 1 800 94 2 400 47 3 500 59 4 600 71 5 700 82 TOTAL 3000 353  

44. ACTIVITY 17 Answer the following. 1. Using the stratified sampling technique, compute the sample size at a 5% margin of error for each hospital listed in the table below. Hospital Population Sample Size A 560 B 284 C 790 D 1,000 E 366 Total

45. ACTIVITY 17 Answer the following. 2. A researcher wants to know the study habits of the students of the College of Physical Therapy in ABC University. Determine the size of the sample units from each level using a 4% margin of error. Year Level Population Sample Size First Year 750 Second Year 600 Third Year 550 Fourth Year 500 Fifth Year 580 Total

46. RANDOM SAMPLING TECHNIQUE or PROBABILITY SAMPLING TECHNIQUE 4. CLUSTER RANDOM SAMPLING It is a random sampling technique which divides a given population into heterogeneous groups called clusters. Heterogeneous group partitions means they are grouped differently according to the controlling variable of the study. The sample is taken through a random selection of cluster(s) and then all members of the chosen cluster(s) will be a part of the sample.

47. EXAMPLE 1. A doctor wants to make a nationwide study on the correlation between smoking and death rate. He decided to focus on the 13 regions of the country, which can be considered as the clusters. If three of the clusters or regions are the desired sample units, the names of the 13 clusters will be written on small pieces of paper, then three will be picked at random using the lottery method. All the residents of the selected three clusters will be included in the study.

48. EXAMPLE 2. A researcher wants to determine who among the families in a small town are using the new detergent product. How is she going to do this using the cluster sampling technique?

49. STRATIFIED VS CLUSTER The difference of cluster sampling from stratified sampling is that the sample consists of elements from the selected clusters only while in stratified sampling, the sample consists of elements from all the strata.

50. RANDOM SAMPLING TECHNIQUE or PROBABILITY SAMPLING TECHNIQUE 5. MULTI-STAGE SAMPLING Here, we use combinations of several random sampling techniques in getting the sample from a very large population. This is done by dividing the whole population by area, and then each area into strata. Thereafter, from each stratum, we get the sample by using the simple random sampling technique.

51. NON-PROBABILITY SAMPLING TECHNIQUE There are some sampling techniques which are biased and therefore not reliable such as those samples drawn by researchers based on their own judgment which are classified as non-probability sampling technique.

52. NON-PROBABILITY SAMPLING TECHNIQUE 1. CONVENIENCE SAMPLING This is used because it is convenient to the researcher. This technique is resorted to by researchers who need the information the fastest way possible.

53. CONVENIENCE SAMPLING EXAMPLE A researcher may find out which detergent is the most popular among households by making phone calls using the phone numbers found in the telephone directory. While the data may easily be obtained, the accuracy of the data may not be reliable since not all households have telephone connections.

54. NON-PROBABILITY SAMPLING TECHNIQUE 2. QUOTA SAMPLING In this method, the researcher uses the proportions of different strata; and from the strata, selections are done using quota. This is most commonly used in opinion polls.

55. QUOTA SAMPLING EXAMPLE Suppose a salesman is required to gather information as to the most common hair shampoo used by female Filipino clients. If he wants 2,000 sample units and he needs to do the survey within a short timetable, he can station himself at a public place, such as park or a mall, then ask the females what shampoo they usually use. After meeting the required number of sample points, the researcher is through with his collection of data.

56. NON-PROBABILITY SAMPLING TECHNIQUE 3. PURPOSIVE SAMPLING The researcher gets his sample from the respondents purposely related or close to him. The respondents of the study will be chosen based on their knowledge of the information required by the researcher.

57. PURPOSIVE SAMPLING EXAMPLE Suppose a researcher wants to make a historical study about Town A. The target population will be the senior citizens of the town since they are the most reliable persons who know the history of the town. If there are 2,000 senior citizens and a 3% margin of error is allowed, the sample size will be 714. They will be chosen using any of the methods discussed previously.

58. GENERALIZATION Answer the following. State and describe the different methods of collecting data. How do we determine the sample size of the given population? State and describe the different sampling techniques.

59. ACTIVITY 18 A. Identify the most appropriate method/s of gathering data to be used in each of the following situations. To determine the causes of death from year 2000 to the present. To identify the factors why students fail in Statistics. To find out the relationship between smoking and lung cancer. To determine the choices of family planning methods of married couples. To determine the average savings of employees of company A in a month.

60. ACTIVITY 18 B. Identify the type of sampling technique used by the researcher in each of the following situations: simple random sampling , systematic random sampling , stratified random sampling or cluster random sampling . 6. The office clerk gave the researcher a list of 500 Grade 10 students. The researcher selected every 20 th name on the list.

61. ACTIVITY 18 7. In a recent research that was conducted in a private school, the subjects of the study were selected by using the Table of Random Numbers. 8. A researcher interviewed people from each town in the province of Albay for his research on population. 9. A researcher is doing a research work on the students’ reaction to the newly implemented curriculum in Mathematics and interviewed every 10 th student entering the gate of the school.

62. ACTIVITY 18 10. A researcher who is studying the effects of educational attainment on promotion conducted a survey of 50 randomly selected workers from each of these categories: high school graduate, with undergraduate degrees, with master’s degree, and with doctoral degree. 11. A researcher selected a sample of n=120 from a population of 850 by using the Table of Random Numbers.

63. ACTIVITY 18 12. A researcher interviewed all top 10 Grade 11 students in each of 15 randomly selected private schools in Metro Manila. 13. A researcher randomly selected 10 barangays in a town for her study. She did this by writing the names of each barangays on a piece of paper which she folded and put in a bowl then she draw 10 pieces of paper from the bowl.

64. ACTIVITY 18 14. A teacher asked her students fall in line. He instructed one of them to select every 5 th student on the line. 15. A researcher chose the subjects of her study by selecting every member of the population. 16. A teacher who is conducting a research on the effects of using calculators in teaching mathematics decided to divide her students into male and female and then she selected students from each gender group.  

65. ACTIVITY 18 17. A Statistics student did a research on the time spent by Grade 11 students in playing video games. He randomly selected his subjects by using the Table of Random Numbers. 18. A statistician selected a sample of n=100 high school students from a private school with 2,500 students. He randomly selected the students from each grade level.

66. ACTIVITY 18 19. A teacher conducted a study in her school to determine who were better in Mathematics: the boys or the girls. 20. A researcher surveyed all diabetic patients in each of the 25 randomly selected hospitals in Metro Manila.