Simple Random SamplingSimple Random SampleSlide 3Slide 4Selecting a Simple Random SampleSlide 6TI-83 – Selecting a SampleExampleGetting a Set of Random NumbersTI-83 – Setting the SeedSlide 11www.random.orgSimple Random SamplingLecture 7Section 2.5Mon, Jan 28, 2008Simple Random SampleSimple Random Sample of size n.Simple Random SampleA consequence of this is that all individuals in the population have the same chance of being selected for the sample.Simple Random SampleHowever, just because a sampling method guarantees that all individuals in the population have the same chance of being in the sample, it does not mean that the sample is a simple random sample.Selecting a Simple Random SampleGiven a population of size N, Number the members from 1 to N.Use a random number generator (such as on a calculator) to generate n random integers from 1 to N.Selecting a Simple Random SampleThe sampling may be done with or w itho ut replacement.If the sampling is done without replacement, then repetitions should be discarded.TI-83 – Selecting a SampleSuppose that the population size is N = 100.Press MATH.Use arrow keys to highlight PRB menu.Press 5 to select randInt (item #5).Enter randInt(1, 100) and press ENTER.A random number appears.Press ENTER repeatedly for more random numbers.ExampleLet the population be the students in this class, numbered 1 – 7 in alphabetical order.So N = 7.Choose a random sample of size n = 3.What is each person’s chance of being selected for the sample?Getting a Set of Random NumbersTo get several random integers at once, possibly with repetitions, use randInt with a third parameter.For example, to get 3 random integers from 1 to 7, enterrandInt(1, 7, 3)TI-83 – Setting the SeedEnter the desired seed, say, 48.Press STO.Press MATH, highlight PRB, select rand (item #1).Press ENTER. The seed is set to 48.ExampleSet the seed to 48.Then select a random sample of size 3 from the population of the previous example.www.random.orgThe web site www.random.org will provide truly random numbers!The numbers are integers ranging over any specified interval.They can be generated with repetitions or without repetitions.You can also do random coin
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