Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Chapter 4
Document related concepts
Transcript
Business Research Methods EMBA-1 1 Business Research Methods EMBA-1 Lecture – 7 Sample Design and Sampling Procedure Determination of Sample Size: A review of Statistical theory 2 Business Research Methods EMBA-1 Sample Design and Sampling Procedure 3 Business Research Methods EMBA-1 Why Sampling Budget and time constraints. Often, Pragmatic reasons Accurate and reliable results Not be possible to contact the whole population Samples are accurate only when researchers have taken care. A sample may be more accurate than a census. In a census there is greater likelihood of non-sampling errors. A small, well-trained, closely supervised group may do a more accurate job Destruction of test units At times testing require the destruction If all tested that way, there would be no product left after testing. Business Research Methods EMBA-1 Stages in Sample Selection Define the target population Select a sample frame Determine if a probability or non probability sample will be chosen Plan procedure for selecting sampling units Determine sample size Select actual sampling units Conduct fieldwork 5 Business Research Methods EMBA-1 Types of Sampling Non Probability Sampling Probability Sampling Business Research Methods EMBA-1 Non Probability Sampling Convenience sampling Judgment sampling Quota sampling Snowball sampling Business Research Methods EMBA-1 Probability Sampling Simple random sampling Systematic sampling Stratified sampling Proportional versus disproportional strata Cluster sampling Business Research Methods EMBA-1 Internet Sampling Internet surveys allow researchers to rapidly reach a large sample. This is both an advantage and a disadvantage. Sample size requirements can be met overnight or in some cases almost instantaneously. A major disadvantage of Internet surveys is the lack of computer ownership and Internet access among certain segments of the population. Business Research Methods EMBA-1 Business Research Methods EMBA-1 Determination of Sample Size: A review of Statistical theory 11 Business Research Methods EMBA-1 Descriptive Statistics Inferential statistics Sample Statistics Population parameters Basic Terminology Statistics used to describe or summarize information about population or sample Statistics used to make inferences or judgments about a population on the basis of a sample Variables in a sample or measures computed from sample data Variables in a population or measured characteristics of a population Business Research Methods EMBA-1 Making the Data Useable Frequency Distribution Percentage distribution Central Tendency Measure of Dispersion Normal Distribution Business Research Methods EMBA-1 Frequency Distribution Percentage distribution Central Tendency Measure of Dispersion Normal Distribution Making the Data Useable Business Research Methods EMBA-1 Making the Data Useable Frequency Distribution Mean Percentage distribution Median Central Tendency Measure of Dispersion Normal Distribution Mode Business Research Methods EMBA-1 Making the Data Useable Frequency Distribution Range Percentage distribution Deviation Scores Central Tendency Variance Measure of Dispersion Standard Deviation Normal Distribution Business Research Methods EMBA-1 Making the Data Useable Frequency Distribution Value of X – Mean Z Percentage distribution = Standard Deviation Central Tendency Measure of Dispersion Normal Distribution Z Mean X Business Research Methods Some Formula EMBA-1 X a small sampling error SMALL SAMPLING E Z cl S X S x S n ERROR Z cl S X X E zs n E 2 18 Business Research Methods EMBA-1 Factors of Sample Size • Variance (standard deviation) • Magnitude of error • Confidence level 19 Business Research Methods EMBA-1 Sample Size Formula - Example Suppose a survey researcher, studying expenditures on lipstick, wishes to have a 95 percent confident level (Z) and a range of error (E) of less than $2.00. The estimate of the standard deviation is $29.00. 20 Sample Size Formula Example Business Research Methods EMBA-1 Suppose a survey researcher, studying expenditures on lipstick, wishes to have a 95 percent confident level (Z) and a range of error (E) of less than $2.00. The estimate of the standard deviation is $29.00. zs n E 2 1.9629.00 2.00 2 2 56.84 2 28 . 42 2.00 808 21 Business Research Methods EMBA-1 Sample Size Formula Example Suppose, in the same example as the one before, the range of error (E) is acceptable at $4.00, sample size is reduced. 22 Sample Size Formula Example Business Research Methods EMBA-1 Suppose, in the same example as the one before, the range of error (E) is acceptable at $4.00, sample size is reduced. zs 1.9629.00 n 4.00 E 2 2 2 56.84 2 14 . 21 4.00 202 23 Business Research Methods Calculating Sample Size EMBA-1 99% Confidence ( 2 . 57 )( 29 ) n 2 74.53 2 2 [37.265] 1389 2 2 ( 2 . 57 )( 29 ) n 4 2 74 . 53 4 2 [18.6325] 347 2 24 Standard Error of the Proportion Business Research Methods EMBA-1 sp pq n or p (1 p ) n 25 Business Research Methods EMBA-1 Confidence Interval Confidence Interval for a Proportion p ZclSp E Z cl S X 2 Z pq n E 2 26 Business Research Methods EMBA-1 2 z pq n E2 Where: n = Number of items in samples Z2 = The square of the confidence interval in standard error units. p = Estimated proportion of success q = (1-p) or estimated the proportion of failures E2 = The square of the maximum allowance for error between the true proportion and sample proportion or zsp squared. 27 Calculating Sample Size at the 95% Confidence Level Business Research Methods EMBA-1 Suppose a simple random sample shows 60% of the respondents (p) recognize the name. Researcher wishes to estimate with 95% confidence (I.e., Z=1.96) that the allowance for sampling error is not more that 3.5% (E). Solution: As given: p .6 q .4 (1. 96 )2(. 6)(. 4 ) n ( . 035 )2 (3. 8416)(. 24) 001225 . 922 . 001225 753 28 Business Research Methods EMBA-1 Any Question? 29 Business Research Methods EMBA-1 Thanks for your contribution 30 Business Research Methods EMBA-1 Assignment Gp Assignment Case-23: Business Forum Industry Submission date is 17th Jul Submission time: 0630 p.m. Selected person will present for 10 mins Discussion to focus, how the data were analyzed 31 Business Research Methods EMBA-1 See You Next Week 32 Business Research Methods EMBA-1 Target population Sample frame Sampling Method Choice Procedure for sampling units Determine sample size Actual sampling units Conduct fieldwork Stages in Sampling What is the relevant population? In many cases this is not a difficult question, but in other cases, the decision may be a difficult one. Answering questions about the crucial characteristics of the population is the usual technique for defining the target population. The question “Whom do we want to talk to?” must be answered. Business Research Methods EMBA-1 Target population Sample frame Sampling Method Choice Procedure for sampling units Determine sample size Actual sampling units Conduct fieldwork Stages in Sampling A sampling frame is a list of elements from which the sample may be drawn. The sampling frame is also called the working population, because it provides the list that can be operationally worked with. Business Research Methods EMBA-1 Stages in Sampling Target population Sample frame Sampling Method Choice Procedure for sampling units Determine sample size Actual sampling units Conduct fieldwork Probability or Non probability sample In probability sampling every element in the population has a known nonzero probability of selection; each member of the population has an equal probability of being selected. In nonprobability sampling, the probability of any particular member of the population being chosen is unknown. Nevertheless, there are occasions when the nonprobability samples are best suited for the researcher’s purpose. Business Research Methods EMBA-1 Stages in Sampling Target population Sample frame Sampling Method Choice Procedure for sampling units Determine sample size Actual sampling units Conduct fieldwork The sampling unit is a single element or group of elements subject to selection in the sample. If the target population has been divided into stages, the term primary sampling unit (PSU), secondary sampling units, or tertiary sampling units is used . When there is no list of population elements, the sampling unit is generally something other than the population element. For example, in a random digit dialing study the sampling unit will be telephone numbers. Business Research Methods EMBA-1 Convenience sampling Judgment sampling Quota sampling Snowball sampling Non Probability Sampling Researchers generally use convenience samples to obtain a large number of completed questionnaires quickly and economically Convenience samples are best utilized for exploratory research when additional research will subsequently be conducted with a probability sample Business Research Methods EMBA-1 Convenience sampling Judgment sampling Quota sampling Snowball sampling Non Probability Sampling Judgment or purposive sampling is a nonprobability technique in which an experienced individual selects the sample upon his or her judgment about some appropriate characteristic required of the sample members Business Research Methods EMBA-1 Convenience sampling Judgment sampling Quota sampling Snowball sampling Non Probability Sampling The purpose of quota sampling is to ensure that the various subgroups in a population are represented on pertinent sample characteristics to the exact extent that the investigators desire Business Research Methods EMBA-1 Convenience sampling Judgment sampling Quota sampling Snowball sampling Non Probability Sampling Snowball sampling refers to a variety of procedures in which initial respondents are selected by probability methods, but additional respondents are then obtained from information provided by the initial respondents. This technique is used to locate members of rare populations by referrals. Business Research Methods EMBA-1 Simple random sampling Systematic sampling Stratified sampling Proportional versus disproportional strata Cluster sampling Probability Sampling A simple random sample is a sampling procedure that assures that each element in the population will have an equal chance of being included in the sample Business Research Methods EMBA-1 Simple random sampling Systematic sampling Stratified sampling Proportional versus disproportional strata Cluster sampling Probability Sampling Systematic sampling is extremely simple: An initial starting point is selected by a random process; then every nth number on the list is selected. Business Research Methods EMBA-1 Probability Sampling Simple random sampling Systematic sampling Stratified sampling Proportional versus disproportional strata Cluster sampling In stratified sampling, a subsample is drawn utilizing a simple random sample within each stratum. The reason for taking a stratified sample is to have a more efficient sample than could be taken on the basis of simple random sampling Business Research Methods EMBA-1 Simple random sampling Systematic sampling Stratified sampling Proportional versus disproportional strata Cluster sampling Probability Sampling If the number of sampling units from each stratum is in proportion to the relative population size of the stratum, the sample is a proportional stratified sample. Business Research Methods EMBA-1 Simple random sampling Systematic sampling Stratified sampling Proportional versus disproportional strata Cluster sampling Probability Sampling The purpose of cluster sampling is to sample economically while retaining the characteristics of a probability sample. In a cluster sample, the primary sampling unit is no, longer the individual element in the population (for example, grocery stores) but a larger cluster of elements located in proximity to one another (for example, cities). The area sample is the most popular type of cluster sample.
