Monday, February 25, 2019
SAMPLE AND SAMPLING TECHNIQUE example ? Is a finite number of an item (or individual) taken from a race having identical characteristics with those of the population from which it was taken. ? A exemplar is considered turned if one or several of the items (or individuals) in the population are given a systematically better opportunity to be chosen than the others. ? A collection with lowtake dimension Sample size ? Random sampling, the larger the hear, the more accurately it represents the population from which it was taken. As the savour size decreases, the degree of representativeness becomes less. Size of sample depends on some factors ? Degree of accuracy required ? Amount of variant inherent in the population from which the sample was taken ? Nature and complexness of the characteristics of the population under consideration Sample Strategy ? Common take Approach ? reconcile what data to collect ? then undertake see ? decide what analysis should be done wrong data pile up ? data serene on wrong subjects ? insufficient data collected ? Desired analysis may non be possible or effective Key to Good Sampling ? formulate the aims of the ingest ? decide what analysis is required to satisfy this aims ? decide what data are required to facilitate the analysis ? collect the data required by the study Determine sample size ? Slovin Formula ? n = N__ ? 1+NE? ? Where n = sample size ? N = population sizeE = margin of error * coveted ExampleWhat should be the representative sample size if the population from which the sample will be taken is 10,000 and the desired margin of error is 2%? SolutionTo determine the sample size, intention the formula n = ___N__ 1+NE? n = 10,000 = 2,000 1+ (10,000) (0. 02)? The sample size is 2,000 This formula in finding the sample size brooknot be used when the normal approximation of the population is poor or small. Margins of misconduct Population 1% 2% 3% 4% 5% 10% 500 * * * * 222 83 1500 * * 638 441 316 94 2500 * 1250 767 500 345 96 3000 * 1364 811 517 353 97 4000 * 1538 870 541 364 98 5000 * 1667 909 556 370 98 6000 * 1765 938 566 375 98 7000 * 1842 959 574 378 99 8000 * 1905 976 580 381 99 9000 * 1957 989 584 383 99 railyard0 5000 2000 1000 588 385 99 50000 8333 2381 1087 617 387 100 Margin of Error Is the allowable error in percent due to the use of the sample, instead of the population ? * indicate that the given of normal approximation is poor and that the sample size formula does not apply. Guidelines with regards to the minimum number of items needed for a representative sample ? descriptive studies a minimum number of 100 ? Co-relational studies a sample of at least 50 is deemed necessary to establish the existence of a blood ? Experimental and causal comparative studies minimum of 30 per group ?sometimes experimental studies with only 15 items in each group can be defended if they are very tightly controlled ? If the sample is randomly selected and is suffi ciently large, an accurate view of the population can be had, provided that no bias enters the selection process Sampling Error ? Is the error attributed to chance that is being made when selecting random samples to represent a given population under consideration. ? It is the expected chance difference, variation or deviation between a random sample and the population. ? Does not result from measurement or count errors, although these errors also contribute to inaccuracy.